How many iron (ii) ions combine with oxygen to form iron (ii) oxide answer?

Iron (II) means that Fe has lost two electron i. e Fe⁺².

We also know that Oxygen normally exists in - 2 oxidation state i. e. O⁻².

And, for a neutral Iron (II) Oxide the overall charge on it must be zero.

So,

+ 2 + (-2) = 0

Means,

For one atom of Fe⁺² we need one atom of O⁻².

FeO

Result:

One Iron (II) ion combines with oxygen to form iron (ii) oxide.