Periodic classification of elements

Consider the isoelectronic species, Na⁺, Mg²⁺, F^–and O^2–. The correct order of increasing length of their radii is _________.

• Mg²⁺ < Na⁺< F^–< O^2-

• O^2-< F^– < Na⁺< Mg²⁺

• O^2- < F^– < Mg²⁺ < Na⁺

• F^– < O^2- < Mg²⁺ < Na⁺

The order of screening effect of electrons of s, p, d and f orbitals of a given shell of an atom on its outer shell electrons is:

• p < d < s > f

• f > d > p > s

• s > p > d > f

• f > p > s > d

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

• F > Cl > Br > I

• F < Cl < Br < I

• F < Cl > Br > I

• F < Cl < Br < I

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

• magnetic quantum number of any element of the period.

• maximum Principal quantum number of any element of the period.

• maximum Azimuthal quantum number of any element of the period.

• an atomic number of any element of the period.

The formation of the oxide ion, O^2– (g), from oxygen atom requires first an exothermic and then an endothermic step as shown below:

O (g) + e– → O^–(g) ; ∆ H = – 141 kJ mol–1

O^– (g) + e– → O^2– (g) ; ∆ H = + 780 kJ mol–1

Thus the process of formation of O^2– in the gas phase is unfavourable even though O^2– is isoelectronic with neon. It is due to the fact that

• O– ion has a comparatively smaller size than an oxygen atom.

• addition of electron in oxygen results in larger size of the ion.

• oxygen is more electronegative.

• electron repulsion outweighs the stability gained by achieving a noble gas configuration.

Electronic configurations of four elements A, B, C and D are given below :

(A) 1s² 2s² 2p¹ (B) 1s² 2s²

(C) 1s² 2s² 2p⁶ 3s¹ (D) 1s² 2s² 2p⁶

Which of the following is the correct order of increasing tendency to lose electron?

• D<B<A<C

• A<B<C<D

• C<A<B<D

• D<A<B<C

In which of the following options order of arrangement does not agree with the variation of property indicated against it?

• B < C < N < O (increasing first ionisation enthalpy)

• Li < Na < K < Rb (increasing metallic radius)

• F>Cl>Br>I (decreasing electronegativity)

Ionic radii vary in

(i) inverse proportion to the effective nuclear charge.

(ii) inverse proportion to the square of effective nuclear charge.

(iii) direct proportion to the screening effect.

(iv) direct proportion to the square of screening effect.

• (i) and (ii)

• (ii) and (iii)

• (i) and (iii)

• (i) and (iv)

The element with atomic number 57 belongs to

• s-block

• p-block

• d-block

• f-block

Find these groups: Locate Lanthanides and Actinides.

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