Question

When naming ionic compounds, when is '-ate' used instead of '-ide'?

Answer 1

See Below

Explanation:

When an element becomes an anion (- charged), it takes on the name "-ide". `Cl_2` becomes two `Cl^-1` ions, those ions are called "Chloride ions". Same for Oxide ions, Bromide ions.

The ending of "-ate" is usually used with certain polyatomic ions. For example, `CH_3COO^-` is acetate ion.

"-ate" is also used when the central atom of a polyatomic ion has a higher oxidation number (usually means more oxygen atoms around it).

For example:
`ClO^-1` - hypochorite ion
`ClO_2^-1` - chlorite ion
`ClO_3^-1` - chlorate ion
`ClO_4^-1` - perchlorate ion

So if there are polyatomic ions that are related and they have different numbers of oxygens, the one with the less number will usually get the ending -ite....and the one with more oxygens will usually get the ending -ate.

In biochemistry, the name -ate usually means the conjugate base of a weak acid. Pyruvate, stearic acid vs. stearate, acetate...these all basically have COOH turning to `COO^-`

Hope that helps.