Class 10 Chemistry Chapter 3 Notes Kerala Syllabus Periodic Table and Electron Configuration Questions and Answers

Students rely on SCERT Kerala Syllabus 10th Standard Chemistry Textbook Solutions and Class 10 Chemistry Chapter 3 Periodic Table and Electron Configuration Notes Questions and Answers English Medium to help self-study at home.

SSLC Chemistry Chapter 3 Notes Questions and Answers Pdf Periodic Table and Electron Configuration

SCERT Class 10 Chemistry Chapter 3 Periodic Table and Electron Configuration Notes Pdf

SSLC Chemistry Chapter 3 Questions and Answers – Let Us Assess

Question 1.
The element X having 3 shells belongs to group 17.
a) Write the subshell electron configuration of this element.
b) To which block does this element belong?
c) What is its period number?
d) Write the molecular formula of the compound formed when X reacts with an atom of element Y which belongs to the third period and has one electron in its p subshell.
Answer:
a) X – 1s²2s²2p⁶3s²3p⁵
b) p block
c) Period – 3
d) X – Valency – 1
Y – Valency – 3 (Y – 1s²2s²2p⁶3s²3p¹)
The molecular formula of the compound formed by the combination of X and Y is YX₃.

Question 2.
A few subshells are given.
3p, 4d, 3f, 2d, 2p
a) Among these, which subshells are not possible?
b) Explain the reason.
Answer:
a) Among the given subshells the subshells which are not possible are 3f, 2d.
b) In third shell there is no f subshell. In second shell, there is no d subshell.

Question 3.
The position of two elements A and B in the periodic table are given. (Symbols are not real)
A – 4^th period and 2^nd group
B – 2^nd period and 16^th group
a) Write the subshell electron configuration of A and B.
b) Write the values of n and l of electrons in the Outermost subshell of A.
c) How many orbitals are there in the subshell of B having the outermost electron? Find it on the basis of magnetic quantum number ‘m’.
d) Write the molecular formula of the compound formed by the combination of A and B.
e) What type of chemical bond is present in this compound?
Answer:
a) A – 1s²2s²2p⁶3s²3p⁶4s²
B – 1s²2s²2p⁴
b) n = 4, l = 0, 1, 2, 3
c) 4
d) Valency of A – 2
Valency of B – 3
The molecular formula of the compound formed by the combination of A and B is A₃B₂.
e) Ionic bond.

Question 4.
The subshell electron configuration of a few elements are written on the basis of noble gas.
(i) [Ne]3s²3p⁶
(ii) [He]2s¹
(iii) [Ar]3d²4s²
(iv) [Kr]5s²
a) Write the complete subshell electron configuration.
b) Find the symbols of these elements with the help of periodic table.
Answer:
a) (i) 1s²2s²2p⁶3s²3p⁶
(ii) 1s²2s¹
(iii) 1s²2s²2p⁶3s²3p⁶3d²4s²
(iv) 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶5s²

b) (i) Ar
(ii) Li
(iii) Ti
(iv) Sr

Question 5.
The last electron of an atom is added to the 3d subshell. There are 7 electrons in this subshell. Answer the following questions regarding this atom.
a) What is its atomic number?
b) Write its complete electron configuration.
c) To which block does it belong?
d) Find its period number.
e) What is its group number?
Answer:
a) 27
b) 1s²2s²2p⁶3s²3p⁶3d⁷4s²
c) d block
d) Period – 4
e) Group – 9

Question 6.
Find the oxidation state of s block elements in the following compounds.
a) Na₂O
b) KBr
c) CaO
d) MgCl₂
Answer:
a) Oxygen – +1
b) Potassium – +1
c) Calcium – +2
d) Magnesium – +2

Question 7.
Which subshell is represented by each pair of the quantum number values given below?
a) n = 1, l = 0
b) n = 2, l = 1
Answer:
a) 1s
b) 2p

Question 8.
A few subshells are given. Find the values of n and l.
a) 2s
b) 4p
c) 3d
d) 5f
Answer:
a) 2s – n = 2, l = 0
b) 4p – n = 4, l = 1
c) 3d – n = 3, l = 2
d) 5f – n = 5, l = 3

Question 9.
The subshell electron configuration of certain elements are given. Write the short form of each using the symbol of corresponding inert gas.
a) 1s²2s²2p⁴
b) 1s²2s²2p⁶3s²3p⁵
c) 1s²2s²2p⁶3s²3p⁶4s¹
d) 1s²2s²2p⁶3s²3p⁶3d⁵4s²
Answer:
a) [He]2s²2p⁴
b) [Ne]3s²3p⁵
c) [Ar]4s¹
d) [Ar]3d⁵4s²

Question 10.
Iron (Fe) takes part in chemical reactions and becomes Fe³⁺ ion. (Atomic number of = 26 ).
a) Write the electron configuration of this ion.
b) Write the chemical formula of the compound formed when this ion combines with sulphate ion (\(\mathrm{SO}_4^{2-}\)).
c) Which is the other oxidation state of this element? Write the electron configuration of the ion thus formed.
d) Iron shows variable oxidation states. Why?
Answer:
a) Fe – 1s²2s²2p⁶3s²3p⁶3d⁶4s²
Fe³⁺ – 1s²2s²2p⁶3s²3p⁶3d⁵

b) Fe³⁺ + SO₄^2- → Fe₂(S0₄)₃

c) +2, Fe²⁺ – 1s²2s²2p⁶3s²3p⁶3d⁶

d) There is only a slight energy difference between the outermost 4s electrons and the penultimate d subshell electrons. So as per the situation, both of them take part in chemical reactions.

Question 11.
A portion of the periodic table is given. Answer the following questions (Symbols are not real).

a) Which element has the lowest ionisation enthalpy?
b) Identify the alkaline earth metal.
c) Which are the d block elements?
d) Which element has the completely filled d subshell?
e) Identify the element having the electron configuration d³4s²?
f) Identify the noble gas.
g) Which element has only 3 electrons in the outermost p subshell?
Answer:
a) C
b) D
c) E and F
d) G
e) E
f) K
g) H

Chemistry Class 10 Chapter 3 Notes Kerala Syllabus Periodic Table and Electron Configuration

Question 1.
The orbit electron configuration of magnesium atom is given.

a) Write down the electron configuration of magnesium.
Answer:
2, 8, 7

b) Electrons are arranged in three orbits (shells) in this element, aren’t they? Which of these orbits has the least energy?
Answer:
K shell

c) Which orbit is the farthest from the nucleus?
Answer:
M shell

d) Which orbit has the maximum energy?
Answer:
M shell

Question 2.
Find out the maximum number of electrons that can be accommodated in L, M and N shells in the same way and record the values in your science diary.
Answer:
The maximum number of electrons that can be accommodated in orbitals of L shell =
\(\frac{\text { Total number of electrons }}{\text { Total number of orbitals in } L \text { shell }}\) = \(\frac{2 n^2}{n^2}\) = \(\frac{2 \times 2^2}{2^2}\) = \(\frac{8}{4}\) = 2
The maximum number of electrons that can be accommodated in orbitals of M shell =
\(\frac{\text { Total number of electrons }}{\text { Total number of orbitals in } M \text { shell }}\) = \(\frac{2 n^2}{n^2}\) = \(\frac{2 \times 3^2}{3^2}\) = \(\frac{18}{9}\) = 2
The maximum number of electrons that can be accommodated in orbitals of N shell =
\(\frac{\text { Total number of electrons }}{\text { Total number of orbitals in } N \text { shell }}\) \(\frac{2 n^2}{n^2}\) = \(\frac{2 \times 4^2}{4^2}\) = \(\frac{32}{16}\) = 2
Now it is clear that the maximum number of electrons that can be accommodated in each orbital = 2n²/n² = 2

Question 3.
Complete the table based on this.

Answer:

Total number of orbitals in each shell is n2. The maximum number of electrons that can be accommodated in each shell is 2n2. The maximum number of electrons that can be accommodated in each orbital is 2. The maximum number of electrons that can be accommodated in each subshell = 2(2l + 1) The maximum number of electrons that can be accommodated in each subshell = s – 2, p – 6, d – 10, f – 14

Question 4.
Similarly, it is possible to represent the other subshells such as p, d, and f.
Complete the table.

Answer:

Question 5.
The maximum number of electrons that can be accommodated in each subshell is given below.
s – 2, p – 6, d – 10, f – 14
Complete the Table based on this.

Answer:

The shells do not have the same energy.
The energy of shells increases in the order. K < L < M < N.
The energy of subshells increases in the following order.
s < p < d < f
In each shell, there is a gradual increase in the energy of a particular subshell.
Example: Is < 2s < 3s < 4s < 5s
The energies of other subshells also vary in this manner.
When electrons are added to a shell in an atom, they will be distributed in various subshells. Electrons are being filled gradually in the subshells in the increasing order of energy. This type of arrangement is known as subshell electron configuration.

When the electrons in an atom are distributed in subshells, they are being filled gradually in the increasing order of energies of the subshells. This is called subshell electron configuration.

Now it is evident that the ascending order of energy of subshells should be known, in order to write the subshell electron configuration. The order of energy can be found from the principal quantum number (n) and azimuthal quantum number (l) values representing each subshell.
The energy of subshells increases in the ascending order of (n + l) values.
On the basis of (n + l) values, let us examine which subshell has greater energy, 1s or 2s.
1s → n = 1, l = 0 (n + l) = 1 + 0 = 1
2s → n = 2, l = 0 (n + l) = 2 + 0 = 2
2s subshell has more energy than 1s subshell.
In this manner, we can find out that 2p subshell has more energy than 2s subshell.
The (n + l) values of 2p and 3s subshells.
2p → n = 2, l = 1 (n + l) = 2 + 1 = 3
3s → n = 3, l = 0 (n + l) = 3 + 0 = 3
Now, it is clear that the (n + l) values of both 2p and 3 s subshells are the same. In such cases, it is considered as the subshell with higher n value has more energy. This means that 3s subshell has more energy than 2p subshell. 3s represents the s subshell of the third shell (M) and 2p represents the p subshell of the second shell (L). It can be seen that on the basis of the distance from the nucleus, the 3 s subshell has more energy than 2p subshell.

Examine which subshell has more energy, 3d or 4s.
3d n = 3, l = 2, n + l = 5
4s n = 4, l = 0, n + l = 4

That is, 4s subshell has lesser energy than 3d subshell. Hence filling of electrons takes place in 3d subshell only after 4s subshell gets filled.

The figure will help you to find the ascending order of energy of various subshells as mentioned above. The subshells in the ascending order of energy is given below.
1s < 2s < 2p < 3s < 3p < 3d < 4p < 5s.
Now, let us see how to write the subshell electron configuration of atoms of various elements.
You know that the only electron of the hydrogen atom gets added to its Is subshell. Thus, the subshell electron configuration of hydrogen atom can be written as 1s¹.

Question 6.
Similarly, what will be the electron configuration of Helium atom (₂He) ?
Answer:
1s²
It is clear that, in Helium atom the 1s subshell gets occupied by the maximum number of electrons that can be accommodated in it.

In the case of the subshell electron configuration of Lithium (₃Li), the electrons get filled in 1s and 2s subshells in the ascending order of energy. ₃Li – 1s¹2s¹

How to read the subshell electron configuration. 1s1 ‘Ones one 1s2 2s1 ‘One s two’ ‘Two s one’

Question 7.
Complete the table by writing the subshell electron configuration of the elements given below.

Answer:

Element	Number of electrons	Subshell electron configuration
4Be	4	1s22s2
5B	5	1s22s22p1
6C	6	1s22s22p2
7N	7	1s22s22p3
8O	8	1s22s22p4
9F	9	1s22s22p5
10Ne	10	1s22s22p6

The p subshell of neon atom is occupied by the maximum number of electrons that it can accomodate.

Question 8.
Write down the subshell electron configuration of elements from ₁₂Mg up to ₁₈Ar in your science diary.
Answer:

Element	Number of electronics	Subshell electron configuration
12Mg	12	1s22s22p63s2
13Al	13	1s22s22p63s23p1
14Si	14	1s22s22p63s23p2
15P	15	1s22s22p63s23p3
16S	16	1s22s22p63s23p4
17Cl	17	1s22s22p63s23p5
18Ar	18	1s22s22p63s23p6

The electron configuration of potassium (₁₉K) is 1s²2s²2p⁶3s²3p⁶4s¹ It is in the s subshell does the last electron gets filled in potassium.
When 3p subshell is completely filled, the next electron is added to the 4s subshell.
3d subshell is having more energy when compared with 4s subshell.

Question 9.
Write the shell wise electron configuration of potassium.
Answer:
₁₉K – 2, 8, 81
M shell of potassium can accommodate more than eight electrons. However, after the first 8 electrons get added to M shell, the next electron goes to the N shell. The reason is now clear to you.

Question 10.
Write down the electron configuration of calcium (₂₀Ca) in the same manner.
Answer:
Shell wise electron configuration – 2, 8, 8, 2
Subshell wise electron configuration – 1s²2s²2p⁶3s²3p⁶4s²

Question 11.
Compare the energies of Is and 2s subshells.
Answer:
Electrons in the 1s subshell have lower energy than electrons in the 2s subshell because they are closer to the nucleus and experience a stronger attraction.

Question 12.
Which subshell has more energy, 3d or 4s?
Answer:
3d subshell has more energy than 4s subshell.

Question 13.
You have learnt that scandium (₂₁Sc) is a transition element. To which shell does the last electron get added in the case of transition elements?
Answer:
N shell

Question 14.
Now, write the shell wise electron configuration of scandium.
Answer:
2, 8, 9, 2
The subshell electron configuration of scandium is in the order 1s²2s²2p⁶3s²3p⁶4s²3d¹.
This is written as 1s²2s²2p⁶3s²3p⁶3d¹4s² in the order of the shell.
That means, as per the order of energy in transition elements, the 4s subshell is completely filled first followed by the gradual filling up of 3d subshell.

Question 15.
Write the electron configuration of the elements that follow, namely ₂₂Ti and ₂₃V.
Answer:

Question 16.
Record the subshell electron configuration of more transition elements in your science diary.
Answer:

Question 17.
So, how will you write the electron configuration of potassium in the same manner?
Answer:
Potassium – 1s²2s²2p⁶3s²3p⁶ 4s¹ – [Ar]4s¹

Question 18.
Similarly write the subshell electron configuration of other elements also.
Answer:

Element	Subshell electron configuration	Short form
Lithium	1s22s1	[He]2s1
Beryllium	1s22s2	[He]2s2
Boron	1s22s22p1	[He]2s22p1
Carbon	1s22s22p2	[He]2s22p2
Sodium	1s22s22p63s1	[Ne]3s1
Magnesium	1s22s22p63s2	[Ne]3s2
Potassium	1s22s22p63s23p64s1	[Ar]4s1
Calcium	1s22s22p63s23p64s2	[Ar]4s2
Scandium	1s22s22p63s23p63d14s2	[Ar]3d14s2
Titanium	1s22s22p63s23p63d24s2	[Ar]3d24s2
Vanadium	1s22s22p63s23p63d34s2	[Ar]3d34s2

This method is commonly used for writing the subshell electron configuration of elements with higher atomic numbers.

Question 19.
Write down the subshell electron configuration of ₂₉Cu.
Answer:
1s²2s²2p⁶3s²3p⁶3d⁹4s²

Question 20.
What change is to be made in the electron configuration of copper in order to attain stability as mentioned above? Note it down.
Answer:
1s²2s²2P⁶3s²3P⁶3d¹⁰4s¹

In the subshell electron configuration of chromium and copper, the configuration with half filled d subshell or completely filled d subshell show greater stability.

Question 21.
With the help of the periodic table, complete the table by finding the blocks to which the given elements belong.

Answer:

The subshell to which the last electron is added will be the same as the block to which the electron belongs. The groups which are included in s block – 1, 2 The groups which are included in p block – 13 to 18 The groups which are included in d block – 3 to 12 f block elements are placed at the bottom of the periodic table in two separate rows.

Question 22.
Write down the shell wise electron configuration of magnesium ( 12 Mg).
Answer:
2, 8, 2

Question 23.
To which period does magnesium belong?
Answer:
Period 3

Question 24.
It is possible to find the period number from subshell electron configuration. Complete the table with the help of periodic table.

Answer:

Element	Subshell electron configuration	The highest shell number	Period number
6C	1s22s22p4	2	2
11Na	1s22s22p63s1	3	3
21SC	1s22s22p63s23p63d14s2	4	4

The period number of an element is the highest shell number in its subshell electron

Question 25.
It is possible to find the group number of elements on the basis of subshell electron configuration. Complete table with the help of periodic table.

Answer:

Group number of s block elements is the number of electrons in the outermost s subshell.

Question 26.
Which are the groups included in p block?
Answer:
Groups 13 to 18
The group number of p block elements is the number obtained by adding the digit 10 (which represents 10 groups of transition elements) to the number of outermost electrons.

Element	Subshell electron configuration	The total number of electrons in the outermost s and p subshells	Group number
5B	1s22s22p1	3	13
14Si	1s22s22p63s23p2	4	14
7N	1s22s22p3	5	15
8O	1s22s22p4	6	16
17Cl	1s22s22p63s23p5	7	17
18Ar	1s22s22p63s23p6	8	18

The group number of p block elements by adding the digit 10 (which represents 10 groups of transition elements) to the number of outermost electrons.

Question 27.
Where are the d block elements placed in periodic table? From which period does d block elements begin?
Answer:
In the periodic table, d-block elements are located in the middle, between groups 2 and 13. They are found in periods 4 to 7 and are included in groups 3 to 12. The d-block begins in the 4th period.

Question 28.
A few d block elements are given in table. Find the group number of these elements with the help of the periodic table and complete the table.

Answer:

The group number of d block elements will be same as the sum of the number of electrons in the outermost s subshell and the number of electrons in the d subshell preceding it.

Question 29.
What happens to the number of shells on moving down a group? (Increases / decreases)
Answer:
Increases

Question 30.
What happens to the attractive force of nucleus on the outermost electrons as the number of shells increases? (Increases/ decreases)
Answer:
Decreases

Question 31.
What happens to the attractive force of nucleus on the outermost electrons with an increase in the nuclear charge? (Increases /decreases)
Answer:
Increases

Question 32.
Though the nuclear charge increases down a group, its influence is overcome by the increase in the number of shells. If so, on moving down a group, does the possibility of donating the outermost electrons increase or decrease?
Answer:
Increases

Ionisation enthalpy decreases on moving down a group.

Let us have a look at how ionisation enthalpy varies along a period.

Question 33.
Is there any change in the number of shells on moving from left to right in a period?
Answer:
No

Question 34.
Does the nuclear charge increase?
Answer:
Yes
Though nuclear charge increases on moving from left to right in a period, there is no change in the number of shells.

Question 35.
How does the attractive force of nucleus on the outermost electrons vary? (Increases / decreases)
Answer:
Increases

Question 36.
If so, how does the ionisation enthalpy change?
Answer:
Increases

On moving from left to right in a period, there is no change in the number of shells. But, nuclear charge increases gradually. The attractive force of the nucleus on the outermost electrons increases. Hence, ionisation enthalpy increases.

Question 37.
Where can you locate the elements with comparatively low ionisation enthalpy in the periodic table?
Answer:
Bottom left of the periodic table
Caesium and Francium are the elements having the least ionisation enthalpy.

Question 38.
Where are the elements having generally higher ionisation enthalpy placed in the periodic table?
Answer:
On the right top of the periodic table
Now it is clear that the ionisation enthalpy of s block elements is relatively lower than that of the elements of other blocks.

Question 39.
Which family of elements has the highest ionisation enthalpy?
Answer:
Noble gas elements

Question 40.
When s bloc! elements take part in chemical reactions, the electrons of outermost s subshell are ……………………………. (donated / accepted / shared)
Answer:
Donated

Question 41.
Find out the oxidation states of s block elements in the compounds given below.
• NaCl
• MgO
Answer:
NaCl – x + – 1 = 0
x = +1
MgO – x + -2 = 0
x = -2

Question 42.
Determine the oxidation states of more s block elements from their compounds and record it in your science diary.
Answer:
Sodium Chloride (NaCl): Sodium (Na) has an oxidation state of +1. and Chlorine (Cl) has -1.
Potassium Hydroxide (KOH): Potassium (K) has an oxidation state of +1, Oxygen (O) has -2. and Hydrogen (H) has +1.

Magnesium Oxide (MgO): Magnesium (Mg) has an oxidation state of +2, and Oxygen (O) has -2.
Calcium Chloride (CaCl₂): Calcium (Ca) has an oxidation state of +2, and Chlorine (Cl) has -1.

The elements of group 1 and group 2 exhibit +1 and +2 oxidation states respectively.

s block elements generally exist in solid state. But Caesium (_5sCs) is a metal having very low melting point (28.40°C). Hence it exists in liquid state on warm days. The elements Francium (₈₇Fr) and Radium (₈₈Ra) are radioactive in nature.

Question 43.
Notice the given portion of the periodic table.

• Which are the groups that include p block elements?
Answer:
p block elements are seen in groups 13 to 18
p block elements include metals, non metals and metalloids. These elements exist in solid, liquid and gaseous states.
Let us see what is the peculiarity in the oxidation state of p block elements as compared to s block elements.

Question 44.
Find the oxidation state of p block elements in the following compounds.
• HF
• Al₂O₃
• SO₂
Answer:
• The oxidation state of F in HF is – 1.
• The oxidation state of O and Al in Al₂O₃ is -2 and +3 respectively.
• The oxidation state of O and S in SO₂ is -2 and +4 respectively.
p block elements exhibit both positive (+) and negative (-) oxidation states.
Gallium is an element having a very low melting point (29.77°C). On warm days, it exist in the liquid state, s block and p block elements are main group elements.

Question 45.
Is the ionisation enthalpy lower for s block elements or p block elements? Explain.
Answer:
s block elements need less energy to lose electrons (lower ionisation enthalpy) than p block elements in the same row because s block elements have fewer outer electrons to lose to become stable, and these electrons are generally held less tightly.

Question 46.
What is the outermost subshell electron configuration of these elements (excluding Cr, Cu)?
Answer:
4s².
Similarly the outermost subshell electron configuration of the elements of 5th period will be generally 5s². The electron configuration of the outermost subshell of d block elements (transition elements) along a period is generally the same (ns^{1 – 2}). Therefore, they show similarities in properties not only within the groups but also along the periods. You have already learnt about this similarity along a period in shell wise electron configuration.

Oxidation states of d block elements:
Ferrous chloride and ferric chloride are two chlorides of iron.
Ferrous chloride FeCl₂
Ferric chloride FeCl₃
The oxidation state of Fe in FeCl₂ is +2.
The oxidation state of Fe in FeCl₃ is +3.
Fe shows variable oxidation states.

Question 47.
The subshell electron configuration of ₂₆Fe is 1s²2s²2p⁶3s²3p⁶3d⁶4s².
How does it change into Fe²⁺?
Answer:
The 2 electrons in the outermost s subshell is donated to form Fe²⁺.

Question 48.
Can you write the subshell electron configuration of Fe²⁺
Answer:
Fe²⁺ – 1s²2s²2p⁶3s²3p⁶3d⁶

Question 49.
How does Fe get +3 oxidation state in FeCl₃?
Answer:
The electrons from outermost s subshell and the penultimate d subshell are lost to form Fe3+

Question 50.
From which subshells are the electrons lost?
Answer:
s subshell and d subshell.

Question 51.
There is only a slight difference between the energies of the outermost s(4s) subshell and the penultimate d(3d) subshell. Hence, from which subshell is the third electron lost along with the two 4s electrons?
Answer:
3d subshell.

Question 52.
You can write the subshell electron configuration of Fe3+ on the basis of this, can’t you?
Answer:
Fe³⁺ – 1s²2s²2p⁶3s²3p⁶3d⁵

Question 53.
The atomic number of manganese (Mn) is 25. Different compounds of manganese are given in the table. Determine the oxidation state of Mn and complete the table.

Answer:

Compound	Oxidation state of Mn	Subshell electron configuration of Mn ion
MnCl2	+2	1s22s22p63s23p63d5
MnO2	+4	1s22s22p63s23p63d3
Mn2O3	+3	1s22s22p63s23p63d4
Mn2O7	+7	1s22s22p63s23p63d6

In transition elements there is only a slight energy difference between the outermost s subshell and the penultimate d subshell. As a result, under favourable conditions, electrons from the d subshell also take part in chemical reactions. That is why transition elements show variable oxidation states.

Coloured compounds:
Among the compounds in a science lab, the coloured compounds are generally of transition elements.
For example: Copper sulphate (CuSO₄ • 5H₂O), potassium permanganate (KMnO₄), potassium dichromate (K₂Cr₂O₇).

The presence of ions of transition elements (eg:- Cu²⁺, CO²⁺) or the ions which contain transition elements (eg:- \(\mathrm{MnO}_4^{-}\), \(\mathrm{Cr}_2 \mathrm{O}_7^{2-}\) ) are generally responsible for the colour of the compounds.
But the compounds of zinc (₃₀Zn) are colourless.

The compounds of transition elements are generally coloured.

Question 54.
Where are the f block elements located in the periodic table.
Answer:
In the periodic table, f-block elements are located at the bottom, separated from the main body of the table.

Question 55.
In which subshell does the filling up of electrons take place in them?
Answer:
Anti penultimate f subshell.
In these elements, filling up of electrons takes place in the anti penultimate shell. They are known as inner transition elements

Question 56.
How are the f block elements of the 6th period known?
Answer:
Actinoids

Question 57.
What about the elements of the 7th period?
Answer:
Lanthanoids

Std 10 Chemistry Chapter 3 Notes – Extended Activities

Question 1.
Write down the subshell electron configuration of elements having atomic number 1 to 30.
Answer:

1. Hydrogen (H, Z = 1): 1s¹
2. Helium (He, Z = 2): 1s²
3. Lithium (Li, Z = 3): 1s²2s¹
4. Beryllium (Be, Z = 4): 1s²2s²
5. Boron (B, Z = 5): 1s²2s²2p¹
6. Carbon (C, Z = 6): 1s²2s²2p²
7. Nitrogen (N, Z = 7): 1s²2s²2p³
8. Oxygen (O, Z = 8): 1s²2s²2p⁴
9. Fluorine (F, Z = 9): 1s²2s²2p⁵
10. Neon ( Ne, Z = 10 ): 1s²2s²2p⁶
11. Sodium (Na, Z = 11 ): 1s²2s²2p⁶3s¹
12. Magnesium (Mg, Z = 12 ): 1s²2s²2p⁶3s²
13. Aluminium (Al, Z = 13 ): 1s²2s²2p⁶3s²3p¹
14. Silicon (Si, Z = 14): 1s²2s²2p⁶3s²3p²
15. Phosphorus ( P, Z = 15): 1s²2s²2p⁶3s²3p³
16. Sulphur ( S, Z = 16): 1s²2s²2p⁶3s²3p⁴
17. Chlorine ( Cl, Z = 17): 1s²2s²2p⁶3s²3p⁵
18. Argon (Ar, Z = 18): 1s²2s²2p⁶3s²3p⁶
19. Potassium ( K, Z = 19): 1s²2s²2p⁶3s²3p⁶4s¹
20. Calcium (Ca, Z = 20): 1s²2s²2p⁶3s²3p⁶4s²
21. Scandium (Sc, Z = 21): 1s²2s²2p⁶3s²3p⁶4s²3d²
22. Titanium ( Ti, Z = 22): 1s²2s²2p⁶3s²3p⁶4s²3d²
23. Vanadium (V, Z = 23): 1s²2s²2p⁶3s²3p⁶4s²3d³
24. Chromium (Cr, Z = 24 ): 1s²2s²2p⁶3s²3p⁶4s¹3d⁵ (Exception due to stability of half-filled d subshell)
25. Manganese (Mn, Z = 25 ): 1s²2s²2p⁶3s²3p⁶4s²3d⁵
26. Iron (Fe, Z = 26 ): 1s²2s²2p⁶3s²3p⁶4s²3d⁶
27. Cobalt (Co, Z = 27 ): 1s²2s²2p⁶3s²3p⁶4s²3d⁷
28. Nickel (Ni, Z = 28): 1s²2s²2p⁶3s²3p⁶4s²3d⁸
29. Copper ( Cu, Z = 29 ): 1s²2s²2p⁶3s²3p⁶4s¹3d¹⁰ (Exception due to stability of fully filled d subshell)
30. Zinc (Zn, Z=30): 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰

Question 2.
Prepare a slide show on the shapes of various orbitals with the help of presentation software.
Answer:
Here are given some hints that you can use to create the slide show
Slide 1: Title
• Title: Where are the Electrons? Shapes of Orbitals.
• Hint: Electrons are not just randomly floating. They hang out in specific areas called orbitals. Let’s see their basic shapes.

Slide 2: The Basic Shapes – ’s’ and ‘p’

• Title: Round and Dumbbell Shapes
• Content:
  • ‘s’ orbital: Round, like a ball around the atom’s center.
  • ‘p’ orbital: Shaped like a dumbbell. There are three ‘p’ orbitals, pointing in different directions.
  • Images: Simple diagrams of a spherical ‘s’ orbital and the three dumbbell-shaped ‘p’ orbitals along x, y, and z axes.
  • Hint: ‘s’ is simple – think of a round balloon, ‘p’ is like tying two balloons together, and we have three of these pointing different ways.

Slide 3: More Complex Shapes – Introducing ‘d’

• Title: A Peek at More Complex ‘d’ Orbitals
• Content: ‘d’ orbitals have more complicated shapes than ‘s’ and ‘p’. There are five of them. We won’t go into detail, but they are more complex.
• Image: A simple image showing one of the’d’ orbital shapes (you can pick a representative one without labeling all five).

Slide 4: Why Shapes Matter

• Title: Why These Shapes are Important
• Content: The shapes of these electron clouds determine how atoms connect and form everything around us.
• Image: A very simple diagram showing two atoms coming together.

Slide 5: Conclusion

• Title: Wrapping Up.
• Content: ‘s’ orbitals are round, ‘p’ orbitals are dumbbell-shaped, and ‘d’ orbitals are more complex. These shapes help us understand how atoms interact.
• Hint: Remember the basic shapes – round ‘s’ and dumbbell ‘p’. These shapes are key to understanding how atoms join together.

Question 3.
Prepare a short note on various fields in which f block elements are used.
Answer:
Here are the hints that can be used to make the short note on various fields in which f-block elements are used:
Lanthanides:
• Metallurgy & Alloys:

• Production of mischmetal for improved steel properties.
• Heat-resistant alloys for high-temperature applications (e.g., jet engines).

• Magnetic Materials:
Creation of powerful permanent magnets (e.g., neodymium and samarium magnets in motors, generators, electronics).

• Catalysis:
Catalysts in petroleum cracking and polymerization

• Medicine & Bio-applications:

• Gadolinium compounds as MRI contrast agents.
• Radioactive isotopes in radiopharmaceuticals for cancer therapy.
• Thorium in cancer treatment (radiotherapy).

• Glass & Ceramics:

• Polishing glass (e.g., cerium oxide).
• Decolorising agents in glass.
• Imparting specific colors to glass and ceramics.

Periodic Table and Electron Configuration Class 10 Notes

Periodic Table and Electron Configuration Notes Pdf

• According to Bohr model of atom, orbits have definite energy and hence they are known as stationary energy levels.
• The regions around the nucleus where there is maximum probability of finding the electrons are called orbitals.
• The numbers which are used to describe the characteristics of orbitals and electrons based on quantum mechanical model of atom are called quantum numbers.
• Principal quantum number (n): Is used to represent the shells or principal energy levels. The possible values for this quantum number are n = 1, 2, 3, 4.n = 1 denotes K shell whereas n = 2 denotes L shell.
• Azimuthal quantum number (l): Defines the three dimensional shape of the orbital. The orbitals having, definite three dimensional shape and oriented towards different directions are clubbed together and considered as subshells. Azimuthal quantum number is also used to represent the subshells of each shell.
• Magnetic quantum number (m): Magnetic quantum number is denoted using the symbol’m’. The quantum number that represents the difference in the orientation of orbitals is called magnetic quantum number. For a particular value of l, there are (2l + 1) values for m.
• Total number of orbitals in each shell is n².
• The maximum number of electrons that can be accommodated in each shell is 2n².
• The maximum number of electrons that can be accommodated in each orbital is 2.
• The maximum number of electrons that can be accommodated in each subshell = 2(2l + 1)
• The maximum number of electrons that can be accommodated in each subshell = s – 2, p – 6 ,d – 10, f – 14
• When the electrons in an atom are distributed in subshells, they are being filled gradually in the increasing order of energies of the subshells. This is called subshell electron configuration.
• The completely filled configuration (d¹⁰) and the half filled configuration (d⁵) are more stable than other configurations.
• In the subshell electron configuration of chromium and copper, the configuration with half filled d subshell or completely filled d subshell show greater stability.
• The subshell to which the last electron is added will be the same as the block to which the electron belongs.
• The groups which are included in s block -1, 2
• The groups which are included in p block – 13 to 18
• The groups which are included in d block – 3 to 12
• f block elements are placed at the bottom of the periodic table in two separate rows.
• The period number of an element is the highest shell number in its subshell electron configuration.
• Group number of s block elements is the number of electrons in the outermost s subshell.
• The group number of p block elements by adding the digit 10 (which represents 10 groups of transition elements) to the number of outermost electrons.
• The group number of d block elements will be same as the sum of the number of electrons in the outermost s subshell and the number of electrons in the d subshell preceding it.
• Ionisation enthalpy decreases on moving down a group.
• On moving from left to right in a period, there is no change in the number of shells. But, nuclear charge increases gradually. The attractive force of the nucleus on the outermost electrons increases. Hence, ionisation enthalpy increases.
• The elements of group 1 and group 2 exhibit +1 and +2 oxidation states respectively.
• Characteristics of p block elements:
  • p block elements include metals, non metals and metalloids. These elements exist in solid, liquid and gaseous states.
  • p block elements exhibit both positive (+) and negative (-) oxidation states.
  • Gallium is an element having a very low melting point (29.77°C). On warm days, it exist in the liquid state.
    s block and p block elements are main group elements.
• Characteristics of d block elements:
  • d-block elements are known as transition elements.
  • They are placed in groups 3 to 12.
  • The electrons are being gradually filled up in the penultimate shell.
  • All the d block elements are metals.
• Characteristics of f block elements:
  • They show variable oxidation states.
  • Actinoids are radioactive elements. These include man-made elements as well.
  • Certain isotopes of elements like Uranium (U), Thorium (Th) and Plutonium (Pu) are used as fuel in nuclear reactors.
  • Neodymium (Nd) is used for making strong magnets.
  • Some elements are used as catalyst in the petroleum industry. For example:- Cerium (Ce), Lanthanum (La).

INTRODUCTION

Get ready to explore the amazing world of atoms and the periodic table. In this chapter, we will learn about quantum numbers, which are like secret codes that tell us where electrons are inside an atom. Then, we will see how electrons fill up different subshells, which helps explain how elements act. We will also discover cool periodic trends in the periodic table – how elements change as we move across and down. Finally, we will look at the different blocks of the periodic table and what makes the elements in each block special. By the end, you will understand why elements are arranged the way they are and why they have the properties they do.

Quantum numbers

• According to Bohr model of atom, orbits have definite energy and hence they are known as stationary energy levels.
• The regions around the nucleus where there is maximum probability of finding the electrons are called orbitals.
• The numbers which are used to describe the characteristics of orbitals and electrons based on quantum mechanical model of atom are called quantum numbers.
• Principal quantum number (n): Is used to represent the shells or principal energy levels. The possible values for this quantum number are n = 1, 2, 3, 4.n = 1 denotes K shell whereas n = 2 denotes L shell.
• Azimuthal quantum number (l): Defines the three dimensional shape of the orbital. The orbitals having, definite three dimensional shape and oriented towards different directions are clubbed together and considered as subshells. Azimuthal quantum number is also used to represent the subshells of each shell.
• Magnetic quantum number (m): Magnetic quantum number is denoted using the symbol’m’. The quantum number that represents the difference in the orientation of orbitals is called magnetic quantum number. For a particular value of l, there are (2l + 1) values for m.
• Total number of orbitals in each shell is n².
• The maximum number of electrons that can be accommodated in each shell is 2n².
• The maximum number of electrons that can be accommodated in each orbital is 2.
• The maximum number of electrons that can be accommodated in each subshell = 2(2l + 1)
• The maximum number of electrons that can be accommodated in each subshell = s – 2, p – 6 ,d – 10, f – 14

Filling of electrons in subshells

• When the electrons in an atom are distributed in subshells, they are being filled gradually in the increasing order of energies of the subshells. This is called subshell electron configuration.
• Each shell has subshells.
• s subshell is common to all shells.
• The energy of shells increases in the order. K < L < M < N.
  The energy of subshells increases in the following order, s < p < d < f
• The subshells in the ascending order of energy is given below. 1s < 2s < 2p < 3s < 3p < 3d < 4p < 5s.
• How to read the subshell electron configuration.
  1s¹ ‘One s one’
  1s² 2s¹ ‘One s two’ ‘Two s one’.
• While writing the electron configuration of an element, the symbol of the noble gas preceding that element is shown within square bracket followed by the electron configuration of the remaining subshell.
• The completely filled configuration (d¹⁰) and the half filled configuration (d⁵ ) are more stable than other configurations.
• In the subshell electron configuration of chromium and copper, the configuration with half filled d subshell or completely filled d subshell show greater stability.
• The subshell to which the last electron is added will be the same as the block to which the electron belongs.
• The groups which are included in s block -1, 2
• The groups which are included in p block – 13 to 18
• The groups which are included in d block – 3 to 12
• f block elements are placed at the bottom of the periodic table in two separate rows.
• The period number of an element is the highest shell number in its subshell electron configuration.
• Group number of s block elements is the number of electrons in the outermost s subshell.
• The group number of p block elements by adding the digit 10 (which represents 10 groups of transition elements) to the number of outermost electrons.
• The group number of d block elements will be same as the sum of the number of electrons in the outermost s subshell and the number of electrons in the d subshell preceding it.

Periodic trend in periodic table

• Ionisation enthalpy decreases on moving down a group.
• On moving from left to right in a period, there is no change in the number of shells. But, nuclear charge increases gradually. The attractive force of the nucleus on the outermost electrons increases. Hence, ionisation enthalpy increases.

Characteristics of elements in various blocks

• The elements of group 1 and group 2 exhibit +1 and +2 oxidation states respectively.
• Characteristics of p block elements:
  • p block elements include metals, non metals and metalloids. These elements exist in solid, liquid and gaseous states.
  • p block elements exhibit both positive (+) and negative (-) oxidation states.
  • Gallium is an element having a very low melting point (29.77°C). On warm days, it exist in the liquid state.
    s block and p block elements are main group elements.
• Characteristics of d block elements:
  • d-block elements are known as transition elements.
  • They are placed in groups 3 to 12.
  • The electrons are being gradually filled up in the penultimate shell.
  • All the d block elements are metals.
• Characteristics of f block elements:
  • They show variable oxidation states.
  • Actinoids are radioactive elements. These include man-made elements as well.
  • Certain isotopes of elements like Uranium (U), Thorium (Th) and Plutonium (Pu) are used as fuel in nuclear reactors.
  • Neodymium (Nd) is used for making strong magnets.
  • Some elements are used as catalyst in the petroleum industry. For example:- Cerium (Ce), Lanthanum (La).

All substances in the universe are composed of atoms of different elements. You have already learnt that the table in which elements are arranged on the basis of their chemical properties is known as the periodic table.

QUANTUM NUMBERS
According to Bohr model of atom, orbits have definite energy and hence they are known as stationary energy levels.

Limitation of Bohr model of atom:
Louis de Broglie discovered the wave nature of matter. This wave nature is highly significant for microscopic particles. In other words, the scientific community has recognised the particle nature as well as the wave nature of electrons. According to Heisenberg’s Uncertainty Principle, it is impossible to determine simultaneously, the exact position and the exact velocity of a fast moving subatomic particle like electron. That is, on the basis of wave particle dual nature and uncertainty principle an electron cannot be considered merely as a particle moving along an orbit.

An atom model that is in line with the dual nature of matter and the uncertainty principle was developed on the basis of quantum mechanics. According to quantum mechanical model of atom, there are regions around the nucleus where there is maximum probability of finding the electrons.

The regions around the nucleus where there is maximum probability of finding the electrons are called orbitals. The numbers which are used to describe the characteristics of orbitals and electrons based on quantum mechanical model of atom are called quantum numbers.

1. Principal quantum number (n)
Principal quantum number (n) is used to represent the shells or principal energy levels. The possible values
for this quantum number are n = 1, 2, 3, 4, ………….
n = 1 denotes K shell whereas n = 2 denotes L shell.

Principal quantum number (n)	1	2	3	4
Shell	K	L	M	N

2. Azimuthal quantum number (l)
Azimuthal quantum number (l) defines the three dimensional shape of the orbital. The orbitals having definite three dimensional shape and oriented towards different directions are clubbed together and considered as subshells. Azimuthal quantum number is also used to represent the subshells of each shell. The subshells are denoted using the symbols s, p, d and f. The number of subshells in a particular shell is equal to the values of n. The value of l ranges from zero to (n – 1). In other words, the value of l can be determined from the value of n.
When n = 1 l = 0
When n = 2 l = 0, 1
l = 0 denotes s subshell, and l = 1 denotes p subshell.

3. Magnetic quantum number (m)
Magnetic quantum number is denoted using the symbol ‘m’. The quantum number that represents the difference in the orientation of orbitals is called magnetic quantum number. For a particular value of l, there are (2l + 1) values for m. When the value of l is zero (l = 0), m can have only one value, that is (2 × 0 + 1 = 1). This shows that s orbital (l = 0) has only one orientation.
l = 1 denotes the p subshell.
Here, m can have 3 values, that is (2 × 1 + 1) = 3. It means that there are three different orientations for p orbitals.
How many values will be there for m when l = 2?
There will be 5 values for m, (2 × 2 + 1) = 5
If so, how many d orbitals are there? …………… 5 ………………..
The total number of orbitals with respect to each shell is given in the table

It is clear that the total number of orbitals in each shell is n².
You have already learnt that the maximum number of electrons that can be accommodated in each shell is 2n².
If so, let us find out the maximum number of electrons that can be accommodated in each orbital.

The maximum number of electrons that can be accommodated in K shell = \(\frac{\text { Total number of electrons }}{\text { Total number of orbitals in } K \text { shell }}\) = \(\frac{2}{1}\) = 2

FILLING OF ELECTRONS IN SUBSHELLS
Each shell has subshells,
s subshell is common to all shells.
Let us represent the subshells along with the serial number (value of n) of the corresponding shell.
The s subshell of K shell (n = 1) can be represented as 1s.
If so, the subshells of the shells L, M, and N be represented as 2s, 3s and 4s respectively.

ANOTHER METHOD OF REPRESENTING SUBSHELL ELECTRON CONFIGURATION
While writing the electron configuration of an element, the symbol of the noble gas preceding that element is shown within square bracket followed by the electron configuration of the remaining subshell.
The electron configuration of sodium is 1s²2s²2p⁶3s¹.The noble gas precedes this element is Neon. Its atomic number is 10. Hence, the electron configuration of sodium can be written including the symbol of neon as [Ne] 3s¹.

THE PECULIARITY OF THE SUBSHELL ELECTRON CONFIGURATION OF CHROMIUM (Cr) AND COPPER (Cu)
The subshell electron configuration of chromium ₂₄Cr – 1s²2s²2p⁶3s²3p⁶3d⁴4s².
But the stable subshell electron configuration of chromium is 1s²2s²2p⁶3s²3p⁶3d⁵4s¹.
The reason for this anomalous electron configuration is that the maximum number of electrons that can be accommodated in a d subshell is 10. It can be represented as d¹⁰. The half-filled d orbital can be represented as d⁵.

The completely filled configuration (d10) and the half filled configuration (d5) are more stable than other configurations In other words, among the electron configuration from d1 to d10, d5 and d10 are more stable. Hence for atoms where the configuration should be d4s2 and d9s2, the filling of electrons takes place such that the configuration becomes d5s1 and d10s1 respectively to attain stability.

HOW TO FIND THE BLOCK FROM SUBSHELL ELECTRON CONFIGURATION

HOW TO FIND THE PERIOD NUMBER FROM SUBSHELL ELECTRON CONFIGURATION
You know how to find the period number from shell wise electron configuration.

PERIODIC TREND IN PERIODIC TABLE
IONISATION ENTHALPY
The ionisation enthalpy of an element is the minimum amount of energy required to remove the most loosely bound electron from the outermost shell of an isolated gaseous atom of the element.
Using periodic table, let us examine how ionisation enthalpy varies on moving down a group.

CHARACTERISTICS OF ELEMENTS IN VARIOUS BLOCKS
CHARACTERISTICS OF s BLOCK ELEMENTS
You know that alkali metals and alkaline earth metals belong to s block.
In these elements, electrons of s subshell take part in chemical reactions.

CHARACTERISTICS OF p BLOCK ELEMENTS

• d-block elements are known as transition elements.
• They are placed in groups 3 to 12.
• The electrons are being gradually filled up in the penultimate shell.
• All the d block elements are metals.
• Elements of the same group show similarities in properties, d block elements also show similarities in properties in their corresponding groups. Have a look at the in which subshell electron configuration of d block elements of 4^th period is given.

CHARACTERISTICS OF f BLOCK ELEMENTS
Characteristics and uses of f block elements:

• They show variable oxidations states.
  Actinoids are radioactive elements. These include man-made elements as well.
• Certain isotopes of elements like Uranium (U), Thorium (Th) and Plutonium (Pu) are used as fuel in nuclear reactors.
• Neodymium (Nd) is used for making strong magnets.
  Some elements are used as catalyst in the petroleum industry. For example:- Cerium (Ce), Lanthanum (La).

Rare earth elements Rare earth elements consist of 17 elements including 15 elements of Lanthanoids along with scandium and yttrium. In reality, they are not so rare in nature as the name indicates. Since they lie scattered on the earth’s surface, it is difficult to find them in large quantities in a particular region. Hence, the process of extracting the metal from its ore is often a challenging task. Rare earth elements have diverse applications in the field of technology. They are used in computers, LCD screens, mobile phones, renewable energy sources, batteries, etc. Monazite, one of the main ores of rare earth metals, is commonly found in the coastal regions of southern Kerala.