Answer:
1.an atom that has gained or lost electrons:
[tex]{ \sf{it \: is \: an \: }}{ \bf{ion}}[/tex]
2. produces OH - ions when added to water:
[tex]{ \sf{it \: is \: a \: }}{ \bf{base}}[/tex]
3. produces H† ions when added to water:
[tex]{ \sf{it \: is \: an \: }}{ \bf{acid}}[/tex]