Question

What is the name of `Co_3N_2`?

Answer 1

Cobalt nitride. or Cobalt +2 nitride.

Explanation:

Cobalt has a common charge of + 2 as in this compound.
Nitrogen has a common charge of -3 as in this compound

Cobalt nitride would be the common name of the compound.

To be more precise the compound should be named Cobalt +2 nitride.
Even more precise the compound can be named tri Cobalt di nitride.

Answer 2

The name is cobalt(II) nitride.

Explanation:

Cobalt is in the `"d"`-block of elements, so it is a transition metal.

Here are the steps for deriving the name of a compound of a transition metal.

Step 1. Write the name of the transition metal

This gives: "cobalt".

Step 2. Add the name of the nonmetal with the ending "-ide"

This gives: "cobalt nitride".

Step 3. Use the charge on the non-metal to find the charge on the transition metal

Each `"N"` needs three electrons to complete its octet.

Thus each `"N"` ion has a charge of -3, and the total charge on the two `"N"` ions is -6.

∴ The total charge on the three `"Co"` ions is +6.

Hence, each `"Co"` ion has a charge of +2.

Step 4. Write the charge on the non-metal as Roman numerals in parentheses immediately after (no spaces) the name of the metal.

This gives the name: cobalt(II) nitride.