Question

why is hydroxide written as OH1- and not OH2? As oxygen's valency is 2- .​

Answer 1

Answer:

Explanation:

Hydroxide means:

Hydroxide ion which is OH- (OH minus)

It carries negative charge.

Oxygen atom initially has 6 valence electrons. One of it combines with the electron from hydrogen to form O-H bond. The oxygen atom (due to its high electronegativity) receives another electron from somewhere else resulting in the "OH-" ion. Now the oxygen atom has 4 electron lone pairs as followed:

Oxygen's electron-hydrogen's electron

Oxygen's electron-somewhere else's electron

Oxygen's electron-oxygen's electron

Oxygen's electron-oxygen's electron

Therefore OH- will generally form another dative bond with another electron-deficient atom like H+ (to form H2O in this case)

*dative bond means oxygen atom donate one of its lone pairs (2 electrons) to another electron-deficient atom to form bond. ( instead of each atom donating one electron to form one electron pair)