Which chemical bond is formed between Mg and Cl atoms during formation of compound MgCl2 ?
a. Covalent bond
b. Ionic bond
c. Coordinate covalent bond
d. Metallic bond

Question

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Correct — option (4), Only b (ionic bond). Magnesium is a metal from Group 2 (the alkaline earth metals) with two electrons in its outermost shell and a low electronegativity, while chlorine is a highly electronegative non-metal from Group 17 that needs just one more electron to complete its outer shell. When magnesium reacts with chlorine, each magnesium atom loses its two outer electrons — one to each of two chlorine atoms — to attain the stable noble-gas electron configuration of neon, while each chlorine atom gains one electron to attain the stable configuration of argon. This complete transfer of electrons, rather than any sharing of them, produces a positively charged magnesium ion (Mg2+) and two negatively charged chloride ions (Cl-), and the compound MgCl2 is held together by the strong electrostatic force of attraction between these oppositely charged ions. That electrostatic attraction between ions formed by complete electron transfer is, by definition, an ionic (or electrovalent) bond, which is exactly what statement b describes. The large electronegativity difference between a Group 2 metal and a Group 17 non-metal is the standard textbook condition for ionic bonding, and MgCl2, like most metal-halide salts, is a classic example of it — a white crystalline solid with a high melting point and good electrical conductivity in the molten or dissolved state, all properties consistent with an ionic lattice.

Why the other options are wrong — (a) A metallic bond is the electrostatic attraction between positive metal ions and a shared 'sea' of delocalised electrons, and it forms only between atoms of metals bonded to each other, as in a block of pure magnesium or an alloy. MgCl2 is a compound between a metal and a non-metal, not metal atoms bonded to other metal atoms, so no metallic bond is involved at all; the bonding here is between Mg2+ and Cl- ions, which is ionic, not metallic.  (b) A covalent bond forms when two atoms — typically two non-metals with comparable electronegativities — share a pair of electrons, as in Cl2 or H2O. Magnesium and chlorine do not share electrons; magnesium's low electronegativity and chlorine's high electronegativity favour a complete transfer of electrons rather than sharing, which is precisely the ionic mechanism, not the covalent one. Selecting covalent bonding here mistakes the general idea of 'atoms bonding' for the specific electron-sharing mechanism that covalency requires.  (c) This combines covalent bonding (already wrong, as explained above) with coordinate covalent bonding, which is also inapplicable here. A coordinate (or dative) covalent bond is a special case of covalent bonding in which both shared electrons come from just one of the two bonding atoms — as seen in the ammonium ion (NH4+) or in ammonia-borane adducts — but it still involves sharing electrons between atoms, not the complete transfer of electrons from a metal to a non-metal. Since MgCl2 forms by electron transfer producing discrete Mg2+ and Cl- ions, neither of the two covalent-type bonds in this pair actually describes it.

Concept: Chemical bonding between two elements is largely governed by the electronegativity difference between them and by how many electrons each needs to reach a stable, noble-gas-like outer shell. When a metal with low ionisation energy (like magnesium) meets a non-metal with high electron affinity (like chlorine), the energetically favourable outcome is for the metal to lose its valence electrons entirely rather than share them, forming a cation, while the non-metal gains those electrons to form an anion. The oppositely charged ions then arrange themselves into a rigid, repeating three-dimensional lattice held together by strong electrostatic (Coulombic) forces — this is ionic bonding. Covalent bonding, by contrast, occurs between atoms of similar electronegativity (typically two non-metals) that share electron pairs rather than transferring them outright, and metallic bonding occurs specifically between metal atoms sharing a common pool of delocalised electrons. MgCl2 is formed from one Group 2 metal and two Group 17 non-metal atoms with a large electronegativity gap, placing it squarely in the ionic category.

State PCS 2025 Q66 — Science & Technology PYQ with Answer

State PCS 2025 Q66 — Science & Technology PYQ with Answer