Assertion (A): Ionisation enthalpies of early actinoids are lower than for early lanthanoids. [2023]

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Q.
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A): Ionisation enthalpies of early actinoids are lower than for early lanthanoids.

Reason (R): Electrons are entering $5 f$ orbitals in actinoids which experience greater shielding from nuclear charge.

In the light of the above statements, choose the correct answer from the option given below: [2023]

1 (A) is true but (R) is false.

2 (A) is false but (R) is true.

3 Both (A) and (R) are true and (R) is the correct explanation of (A).

4 Both (A) and (R) are true but (R) is not the correct explanation of (A).

Ans.
(3)

Early actinoids have low ionisation enthalpy than early lanthanoids because $5 f$ electrons have more effective shielding from nuclear charge than $4 f$ electrons.

Solution

1 (A) is true but (R) is false.

2 (A) is false but (R) is true.

3 Both (A) and (R) are true and (R) is the correct explanation of (A).

4 Both (A) and (R) are true but (R) is not the correct explanation of (A).

Ans.
(3)

Early actinoids have low ionisation enthalpy than early lanthanoids because $5 f$ electrons have more effective shielding from nuclear charge than $4 f$ electrons.

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Solution

1 (A) is true but (R) is false.

2 (A) is false but (R) is true.

3 Both (A) and (R) are true and (R) is the correct explanation of (A).

4 Both (A) and (R) are true but (R) is not the correct explanation of (A).

Ans. (3) Early actinoids have low ionisation enthalpy than early lanthanoids because 5f electrons have more effective shielding from nuclear charge than 4f electrons.

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Ans.
(3)

Early actinoids have low ionisation enthalpy than early lanthanoids because $5 f$ electrons have more effective shielding from nuclear charge than $4 f$ electrons.