The covalent alkaline earth metal halide (X = Cl, Br, I) is

Engineering

Chemistry

Fajans Rule and Its Application

Alkali Metals and Properties

Alkaline Earth Metals and Properties

Question

The covalent alkaline earth metal halide (X = Cl, Br, I) is

MgX₂

BeX₂

SrX₂

CaX₂

The direct monomer of Nylon-6 is caprolactum which polymerises to give Nylon-6 as follows:

The covalent alkaline earth metal halide is BeX₂ (where X = Cl, Br, I).

Alkaline earth metals (Group 2 elements) typically form ionic compounds due to their low ionization energies. However, beryllium (Be) is an exception because of its small atomic size and high ionization energy. This results in a high polarizing power, which distorts the electron cloud of the anion (halide ion), leading to covalent character in its compounds.

The covalent nature can be explained using Fajans' rules:

Small cation size: Be²⁺ has a very small ionic radius.
High charge on cation: Be has a +2 charge.
Large anion size: Halides like Cl^-, Br^-, I^- are relatively large.

This combination increases polarization, making BeX₂ covalent. In contrast, MgX₂, CaX₂, and SrX₂ are ionic due to larger cation sizes and lower polarizing power.

Related topics: Anomalous behavior of beryllium, Fajans' rules, and covalent character in ionic compounds.

Formulae: Polarizing power ∝ (charge / radius) of cation.

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