The statement that is not correct for periodic classification of elements is:

(i) The properties of elements are periodic function of their atomic numbers.

(ii) Non metallic elements are less in number than metallic elements.

(iii) For transition elements, the 3d-orbitals are filled with electrons after 3p-orbitals and before 4s-orbitals.

(iv) The first ionisation enthalpies of elements generally increase with increase in atomic number as we go along a period.

The element expected to form largest ion to achieve the nearest noble gas configuration is:
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The order of electron gain enthalpy in kJ/mol of fluorine, chlorine, bromine and iodine, respectively are
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The correct order of the ionic radii of O²⁻, N³⁻, F⁻, Mg²⁺, Na⁺ and Al³⁺ is:

3.31. The first (ΔiH₁) and the second (ΔiH₂) ionization enthalpies (in kJ mol^–1) and the (Δ_egH) electron gain enthalpy (in kJ mol^–1) of a few elements are given below:

Elements      ΔH1      ΔH2       Δ_egH

I                    520       7300      –60

II                  419        3051     –48

III               1681        3374     –328

IV               1008        1846     –295

V                 2372       5251       +48

VI                 738       1451        –40

Which of the above elements is likely to be:

(a) The least reactive element

(b) The most reactive metal

(c) The most reactive non-metal

(d) The least reactive non-metal

(e) The metal which can form a stable binary halide of the formula MX₂ (X = halogen)

(f) The metal which can form a predominantly stable covalent halide of the formula MX (X = halogen)?

Electronic configuration of some elements is given in Column I and their electron gain enthalpies are given in Column II. Match the electronic configuration with electron gain enthalpy.