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7
MCQ (Single Correct Answer)

Among halogens, the correct order of amount of energy released in electron gain (electron gain enthalpy) is

A
$\mathrm{F}>\mathrm{Cl}>\mathrm{Br}>\mathrm{I}$
B
$\mathrm{F}<\mathrm{Cl}<\mathrm{Br}<\mathrm{I}$
C
$\mathrm{F}<\mathrm{Cl}>\mathrm{Br}\rangle \mathrm{I}$
D
$\mathrm{F}<\mathrm{Cl}<\mathrm{Br}<\mathrm{I}$
8
MCQ (Single Correct Answer)

The period number in the long form of the periodic table is equal to

A
magnetic quantum number of any element of the period
B
atomic number of any element of the period
C
maximum principal quantum number of any element of the period
D
maximum azimuthal quantum number of any element of the period
9
MCQ (Single Correct Answer)

The elements in which electrons are progressively filled in $4 f$-orbital are called

A
actinoids
B
transition elements
C
lanthanoids
D
halogens
10
MCQ (Single Correct Answer)

Which of the following is the correct order of size of the given species

A
I $>\mathrm{I}^{-}>\mathrm{I}^{+}$
B
$\mathrm{I}^{+}>\mathrm{I}^{-}>\mathrm{I}$
C
$\mathrm{I}>\mathrm{I}^{+}>\mathrm{I}^{-}$
D
$\mathrm{I}^{-}>\mathrm{I}>\mathrm{I}^{+}$
11
MCQ (Single Correct Answer)

The formation of oxide ion $0^{2-}(\mathrm{g})$, from oxygen atom requires first an exothermic and then an endothermic step as shown below

$$\begin{aligned} & \mathrm{O}(g)+e^{-} \rightarrow \mathrm{O}^{-}(g) ; \Delta H^{\mathrm{s}}=-141 \mathrm{~kJ} \mathrm{~mol}^{-1} \\ & \mathrm{O}^{-}(g)+e^{-} \rightarrow \mathrm{O}^2(g) ; \Delta H^{\mathrm{s}}=+780 \mathrm{~kJ} \mathrm{~mol}^{-1} \end{aligned}$$

Thus, process of formation of $\mathrm{O}^{2-}$ in gas phase is unfavourable even though $\mathrm{O}^{2-}$ is isoelectronic with neon. It is due to the fact that

A
oxygen is more electronegative
B
addition of electron in oxygen results in larger size of the ion
C
electron repulsion outweighs the stability gained by achieving noble gas configuration
D
$\mathrm{O}^{-}$ion has comparatively smaller size than oxygen atom
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