A pair among the following that have the same size is:

1. Fe²⁺, Ni²⁺

2. Zr⁴⁺, Ti⁴⁺

3. Zr⁴⁺ , Hf⁴⁺

4. Zn²⁺, Hf⁴⁺

The correct order of increasing electron gain enthalpy with a negative sign for the elements O, S, F, and Cl is : 

1. Cl < F < S < O                   

2. O < S < F < Cl

3. F < S < O < Cl                   

4. S < O < Cl < F

With which of the following electronic configuration an atom has the lowest ionisation enthalpy?

(1) 1s²2s²2p⁵                 

(2) 1s²2s²2p³

(3) 1s²2s²2p⁶3s¹           

(4) 1s²2s²2p⁶

Consider the following electronic configuration of an element (P) :

$\left[\mathrm{Xe}\right]4{\mathrm{f}}^{14}5{\mathrm{d}}^{1}6{\mathrm{s}}^2$

The correct statement about element 'P' is :

1. It belongs to the 6th period and the 1st group.

2. It belongs to the 6th period and the 2nd group.

3. It belongs to the 6th period and the 3rd group.

4. None of the above.

Consider the following information about element P and Q :

                        Period number            Group number

P                               2                                 15

Q                               3                                 2

Then formula of the compound formed by P and Q element is :

(1) PQ         

(2) $P_3{Q}_2$           

(3)$Q_3{P}_2$            

(4)$P{Q}_2$

An electronic configuration representing an atom in the excited state is: 

$1.$ $1{\mathrm{s}}^2,2{\mathrm{s}}^{2}2{\mathrm{p}}^1$ $$ $$ $$ $$ $$ $$ $$ $$ $$ $$ $$ $$ $$ $$ $$ $$ $$ $$ $$ $$ $$
$2.$ $1{\mathrm{s}}^2,2{\mathrm{s}}^{2}2{\mathrm{p}}^2$
$3.$ $1{\mathrm{s}}^2,2{\mathrm{s}}^{2}2{\mathrm{p}}^2,3{\mathrm{s}}^1$ $$ $$ $$ $$ $$ $$ $$ $$ $$ $$ $$ $$ $$
$4.$ $1{\mathrm{s}}^2,2{\mathrm{s}}^{2}2{\mathrm{p}}^5$

How does the energy gap between successive energy levels in an atom vary from low to high n values?

(1) All energy gaps are the same

(2) The energy gap decreases as  n increases

(3) The energy gap increases as  n  increases 

(4) The energy gap changes unpredictably as  n  increases

In alkaline earth metals, the properties, from the following, that will increase from Be to Ba are-

(i) Atomic radius       
(ii) Ionisation energy       
(iii) Nuclear charge

Aqueous solutions of two compounds $M_1-O-H and M_2-O-H$ are prepared in two different beakers. If, the electronegativity of $M_1=3.4 , M_2=1.2, O=3.5 and H=2.1,$ then the nature of two solutions will be respectively:

(a) acidic, basic             (b) acidic, acidic

(c) basic, acidic             (d) basic, basic

Which of the following orders of ionic radii is correctly represented?

1. H^->H>$H^{+}$

2. Na⁺>F^->O^2-

3. F^->O^2->Na⁺

4. N^3->Mg²⁺<Al³⁺