How many potassium and nitrogen ions are needed to form an ionic compound?

Click to Flip

Question

What are the charges of the ions formed by potassium (K) and nitrogen (N) when they react?

Answer

Potassium forms a +1 cation (K⁺). Nitrogen forms a -3 anion (the nitride ion, N³⁻).

Question

What is the primary rule for determining the formula of an ionic compound?

Answer

The compound must be electrically neutral. The total positive charge must equal the total negative charge.

Question

How do you calculate the simplest ratio of K⁺ to N³⁻ ions needed for a neutral compound?

Answer

The +1 charge of K⁺ and -3 charge of N³⁻ have a lowest common multiple of 3. Therefore, you need 3 K⁺ ions (+3 total) for every 1 N³⁻ ion (-3 total).

Question

What is the name and chemical formula of the ionic compound formed between potassium and nitrogen?

Answer

Potassium nitride, with the formula K₃N.

Question

Why would a compound with the formula "KN" (one K⁺ and one N³⁻) not be stable?

Answer

It would have a net charge of -2 [(+1) + (-3) = -2], violating the rule of electrical neutrality for ionic compounds.

1 / 3

Does a single potassium ion (K⁺) carry the same magnitude of charge as a single nitride ion (N³⁻)?

Three potassium ions and one nitrogen ion are needed.