What Is the Valency of Bromide Ion?

The valency of an ion refers to its ability to combine with other atoms or ions, determined by the number of electrons it can gain, lose, or share to achieve a stable electron configuration. The bromide ion (Br⁻) is formed when a bromine atom gains one electron, resulting in a negative charge.

Electron Configuration and Formation

Bromine is a halogen, found in Group 17 of the periodic table. Its electronic configuration is [Ar] 3d¹⁰ 4s² 4p⁵, meaning it has seven electrons in its outermost shell. To achieve a stable octet, bromine needs one more electron. When it gains this electron, it becomes the bromide ion (Br⁻), which has a complete octet in its valence shell.

Valency Explained

• Bromine Atom (Br): 7 valence electrons, needs 1 more to complete the octet.
• Bromide Ion (Br⁻): Gains 1 electron, achieving 8 valence electrons.
• Valency: The valency of the bromide ion is 1, as it can form one bond by accepting a single electron.

Chemical Behavior

Bromide ions are highly reactive due to their tendency to achieve a stable electron configuration. In compounds such as sodium bromide (NaBr) or potassium bromide (KBr), the bromide ion pairs with a positively charged ion (cation) to form stable ionic compounds.

Visual Representation

The Lewis dot structure for the bromide ion shows eight dots (electrons) around the Br symbol, enclosed in brackets with a negative sign, indicating the extra electron and negative charge.

Key Takeaways

• Valency of bromide ion is 1 because it gains one electron to complete its octet.
• Bromide ions are common in various salts and are essential in many chemical and biological processes.