NEET Practice Questions (MCQs) with Answers & Solutions

n-1  = grp 17

n - 2 = grp 16

n + 1 = grp 1

n + 2 = grp 2

so grp 17  will have highest I.E

Addition of 2nd electron is always endothermic.

(a)

For option (a)

First ionisation energy is the energy required to remove an electron from outermost shell.

Hence, correct order is B < C < O < N.

For option (b)

Electron gain enthalpy is the energy required to gain an electron in the outermost shell.

Hence, the correct order is I < Br < F < Cl.

For option (c)

As we move down the group in alkali metal, metallic radius increases Li < Na < K < Rb.

For option (d)

In case of isoelectronic species, as positive charge decreases or negative charge increases the ionic size of the species increases and vice-versa Al³⁺ < Mg²⁺ < Na⁺ <F^- .

            Ca²⁺ < K⁺ < Ar
Ar , K⁺ and Ca²⁺ are isoelectronic i.e. with same number of electrons. 18. For isoelectronic species ionic radii decreases with increase in effective (relative) positive charge. Also Ar, K and Ca belong to the same period (3rd period).

(a) Since, electron repulsion predominate over the stability gained by achieving noble gas configuration. Hence, fomation of O^2- in gas phase is unfavourable.

(a) H^->H>H+

It is known that radius of a cation is always smaller than that of a neutral atom due to decrease in the number of orbits. Whereas, the radius of anion is always greater than a cation due to decrease in effective nuclear charge.

(b) Na⁺>F^->O^2-

The given species are isoelectronic as they contain same number of electrons. For isoelectronic species,

      ionic radii $\propto$ 1/atomic number

                   Ion: Na⁺ F^- O^2-

Atomic number:    11  9   8 

Hence, the correct order of ionic radii is O^2->F^->Na⁺

(c) Similarly, the correct option is O^2->F^->Na⁺

(d) Ion            :        Al³⁺  Mg²⁺     N^3-

Atomic number:         13     12        7

Hence, the correct order is N^3->Mg²⁺>Al³⁺

Isoelectronic species contain same number of electrons Be²⁺ contains 2 electrons. Among the given options, only Li⁺ contains 2 electrons and therefore, it is isoelectronic with Be²⁺.

H⁺ $\to$no electron; Na⁺ $\to$ 10e^-

Li⁺ $\to$ 2e^-;  Mg2⁺ $\to$ 10e^-

Hence, Be²⁺ is isoelectronic with Li⁺

(d) Ionic compounds are more soluble in water or in an aqueous medium

Ionic character $\propto$size of cation (if anion is same)

The order of size of cation is

             Na⁺>Zn²⁺>Cu²⁺

.^.. The order of ionic character and hence of solubility in water is as

                    Na₂S>ZnS>CuS

Ease of adsorption of the hydrated alkali metal ions on an ion-exchange resins decreases as the size of alkali metal ions increases.

Since, the order of size of alkali metal ions

           Li⁺<Na⁺<K⁺<Rb⁺

Thus, the ease of adsorption follows the order

         Rb⁺<K⁺<Na⁺<Li⁺