Question

Explain the bond formation in BeCl₂ and MgCl₂ . BeCl₂ bond formation:

Answer 1

1. Electronic confiuration of Be(Z = 4) is 1s² 2s² and electronic configuration of Cl (Z = 17) is 1s² 2s² 2p⁶ 3s² 3p⁵ .

2. Beryllium has 2 electrons in its valence shell and chlorine atoms (2) have 7 electrons in their valence shell.

3. By losing two electrons, Beryllium attains the inert gas configuration of Helium and becomes a dipositive cation, Be²⁺ and each chlorine atom accepts one electron to become (Cl^-) uninegative anion and attains the stable electronic configuration of Argon.

4. Then Be²⁺ combine with 2Cl ions to form an ionic crystal in which they are held together by electrostatic attractive forces.

5. During the formation of 1 mole of BeCl₂ , the amount of energy released is – 468 kJ/mol. This favours the formation of BeCl, and its stabilisation.

MgCI₂ bond formation:

1. Electronic configuration of Mg (z = 12) is 1s² 2s² 2p⁶ 3s² .

Electronic configuration of Cl (z = 17) is 1s² 2p⁶ 3p⁶ 3p⁵

2. Magnesium has 2 electrons in its valence shell and chlorine has 7 electrons in its valence shell.

3. By losing two electrons, magnesium attains the inert gas configuration of Neon and becomes a dipositive cation (Mg²⁺) and two chlorine atoms accept these electrons to become two uninegative anions [2Cl^-] by attaining the stable inert gas configuration of Argon.

4. These ions, Mg²⁺ and 2Cl^- combine to form an ionic crystal in which they are held together by electrostatic attractive forces.

5. The energy released during the formation of 1 mole of MgCl₂ is –783 kJ/mole. This favours the formation of MgCI₂ and its stabilisation.