Which of the following compounds is an example of an electrovalent bond?

Analysis

The question asks us to identify which of the given compounds is formed by an electrovalent bond (also known as an ionic bond).

Concept Explanation

An electrovalent (ionic) bond is formed through the complete transfer of electrons from one atom to another. This typically occurs between:

• Metals (which lose electrons to become positive ions/cations)
• Non-metals (which gain electrons to become negative ions/anions)

In contrast, covalent bonds (found in options B, C, and D) are formed by the sharing of electrons between non-metal atoms.

Step-by-Step Solution

1. Analyze NaCl: Sodium (Na) is a Group 1 metal. Chlorine (Cl) is a Group 7 non-metal. Sodium transfers one electron to Chlorine to achieve a stable octet configuration. This electrostatic attraction between the resulting $Na^+$ and $Cl^-$ ions forms an ionic (electrovalent) bond.
2. Analyze $CO_2$: Carbon and Oxygen are both non-metals. They share electrons to form covalent bonds.
3. Analyze $H_2O$: Hydrogen and Oxygen are both non-metals. They share electrons to form covalent bonds.
4. Analyze $CH_4$: Carbon and Hydrogen are both non-metals. They share electrons to form covalent bonds.

Since NaCl is the only compound formed by the transfer of electrons between a metal and a non-metal, it is the only electrovalent compound listed.

Identification of Answer

The correct option is A.

Exam Tip

A quick way to spot an electrovalent compound in JAMB Chemistry is to look for a compound containing a Group 1 or Group 2 metal bonded to a non-metal. If you see only non-metals (like C, H, O, N, S), it is almost certainly a covalent compound!