Classification of Elements and Periodicity in Properties

The one electron species having ionisation energy of 54.4 eV is

• He⁺

• H

• Be²⁺

• Be³⁺

Ionisation energy in group 1A varies in the decreasing order as

• Li > Na > K > Cs

• Na > Li > K > Cs

• Li > Cs > K  Na

• K > Cs > Na > Li

An example of a non-stoichiometric compound is

• PbO

• NiO₂

• Al₂O₃

• Fe₃O₄

The equation used to represents the electron gain enthalpy is

• X(g) + e^- → X^-(g)

• X(s) + e^- → X^-(g)

• X(g) → X⁺(g) + e^-

• X(s) → X⁺(g) + e^-

An element in +2 oxidation state has 24 electrons. The atomic number of the element and the number of unpaired electrons in it respectively are

• 24 and 4

• 26 and 4

• 24 and 2

• 26 and 5

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