Question 39 of 48advanced🔍 AnalyzeLong Answer5 marks

The first (ΔᵢH₁) and the second (ΔᵢH₂) ionization enthalpies (in kJ mol⁻¹) and the (Δeg H) electron gain enthalpy (in kJ mol⁻¹) of a few elements are given below: Elements: I (ΔH₁: 520, ΔH₂: 7300, ΔegH: -60), II (ΔH₁: 419, ΔH₂: 3051, ΔegH: -48), III (ΔH₁: 1681, ΔH₂: 3374, ΔegH: -328), IV (ΔH₁: 1008, ΔH₂: 1846, ΔegH: -295), V (ΔH₁: 2372, ΔH₂: 5251, ΔegH: +48), VI (ΔH₁: 738, ΔH₂: 1451, ΔegH: -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)?

(a)
Answer

Element V is the least reactive element because it has the highest first ionization enthalpy (23722372 kJ mol−1^{-1}) and a positive electron gain enthalpy (+48+48 kJ mol−1^{-1}), characteristic of a noble gas with a completely filled shell.

(b)
Answer

Element II is the most reactive metal as it has the lowest first ionization enthalpy (419419 kJ mol−1^{-1}) and a very high second ionization enthalpy, readily losing one electron to form a cation.

(c)
Answer

Element III is the most reactive non-metal due to its highest negative electron gain enthalpy (−328-328 kJ mol−1^{-1}), readily accepting an electron to form an anion.

(d)
Answer

Element IV is the least reactive non-metal because its electron gain enthalpy (−295-295 kJ mol−1^{-1}) is less negative than Element III, making it less eager to gain electrons.

(e)
Answer

Element VI can form a stable binary halide of the formula MX2MX_2 because it has relatively low first (738738 kJ mol−1^{-1}) and second ionization enthalpies (14511451 kJ mol−1^{-1}), allowing it to easily lose two electrons.

(f)
Answer

Element I can form a predominantly stable covalent halide of the formula MXMX. It has a low first ionization enthalpy (520520 kJ mol−1^{-1}) and a very high second ionization enthalpy (73007300 kJ mol−1^{-1}), indicating a +1+1 valency. Its small size leads to high polarizing power, favoring covalent character.

Explanation

The reactivity and bonding nature of elements can be predicted using their ionization enthalpies and electron gain enthalpies. Noble gases are least reactive due to high ionization enthalpy and positive electron gain enthalpy (Element V). Alkali metals are highly reactive metals due to very low first ionization enthalpy (Element II). Halogens are highly reactive non-metals due to highly negative electron gain enthalpy (Element III). Group 16 elements are less reactive non-metals than halogens (Element IV). Alkaline earth metals form MX2MX_2 halides as their first two ionization enthalpies are comparatively low (Element VI). Lithium (Element I) forms covalent halides due to its small size and high polarizing power despite being an alkali metal.

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