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Classification of Elements and Periodicity in Properties

Multiple Choice Questions

31.

An f-shell containing 6 unpaired electrons can exchange

6 electrons
9 electrons
12 electrons
15 electrons

32.

Among the elements Ca, Mg, P and Cl, the order of increasing atomic radii is

Mg< Ca< Cl< P
Cl <P <Mg< Ca
P <Cl< Ca< Mg
Ca <Mg <P < Cl

33.

Among the following which one has the highest cation of anion size ratio?

34.

What is the value of electron gain enthalpy of Na if IE₁ of Na = 5.1 eV?

-5.1 eV
-10.2 eV
+2.55 eV
+10.2eV

35.
Assertion (A): K, Rb and Cs form superoxides.
Reason (R): The stability of the superoxides increases from 'K' to 'Cs' due to decrease in lattice energy.
The correct answer is

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

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

(A) is true but (R) is not true

(A) is not true but (R) is true

(A) is true but (R) is not true

Superoxides are the species having an $O - O$ bond and O in an oxidation state of $- \frac{1}{2}$ (superoxide ion is $O_{2}^{-}$ ). Usually these are formed by active metals such as KO₂, RbO₂ and CsO₂. For the salts of larger anions (like $O_{2}^{-}$ ), lattice energy increases in a group. Since, lattice energy is the driving force for the formation of an ionic compound and its stability, the stability of the superoxides from 'K' to 'Cs' also increases.