Among the following, the isoelectronic specie (s) is/are

(i)  O^2-, F^-, Na⁺, Mg²⁺

(ii) Na⁺, Mg⁺, Al³⁺, F^-

(iii) N^3-,  O^2-, F^-, Ne

• (i) and (ii)

• (i), (ii) and (iii)

• (ii) and (iii)

• (i) and (iii)

What is the atomic number of the element with symbol Uus?

• 117

• 116

• 115

• 114

The increasing order of the first ionisation enthalpies of the elements B, P, S and F is 

• B < S < P < F

• F < S < P < B

• P < S < B < F

• B < P < S < F

The electronic configuration of ₅₉Pr ( praseodimium) is

• [₅₄Xe] 4f²5d¹6s²

• [₅₄Xe] 4f¹5d¹6s²

• [₅₄Xe] 4f³6s²

• [₅₄Xe] 4f³5d²

The size of the iso-electronic species Cl^-, Ar and Ca²⁺ is affected by:

• nuclear charge

• Prinicpal quantum number of valence shell

• azimuthal quantum number of valence shell

• electron-electron interaction in the outer orbitals

Among the following species, the diamagnetic molecule is:

• B₂

• O₂

• CO

• NO

The element having greatest difference between its first and second ionization energies, is

• K

• Ca

• Ba

• Sc

208.

The electronic configuration of Eu (Atomic no.63), Gd (Atomic no. 64) and Tb (Atomic no. 65) are

• [Xe]4f⁶ 5d¹ 6s², [Xe] 4f⁷ 5d¹ 6s² and [Xe] 4f⁹  6s² 

• [Xe] 4f⁶ 5d¹ 6s² , [Xe] 4f⁷ 5d¹ 6s² and [Xe] 4f⁸ 5d¹ 6s² 

• [Xe] 4f⁷  6s², [Xe] 4f⁷ 5d¹ 6s² and [Xe] 4f⁹ 6s² 

• [Xe] 4f⁷  6s², [Xe] 4f⁷ 5d¹ 6s² and [Xe] 4f⁹ 6s² 

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

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

• I<Br<Cl<F(increasing electron gain enthalpy)

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

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

The species Ar, K⁺ and Ca²⁺ contain the same number of electrons. In which order do their radii increase?

• Ar < K⁺< Ca²⁺

• Ca²⁺ < Ar < K⁺

• Ca²⁺ < K⁺ < Ar

• Ca²⁺ < K⁺ < Ar