Answer: A. atoms that have lost or gained an electron and have a charge.
Step-by-step explanation:
- Whenever an atom carries a charge which is non zero, it is said to be an ion.
- An ion can be positively charged if it loses an electron and is called a cation.
- An ion can also be negatively charged if it gains an electron and is called an anion.
- An example of a cation is sodium ion, Na+ which is formed due to the loss of one electron.
- An example of an anion is chloride ion, Cl- which is formed due to the gain of one electron.