Explanation:
When an atom gains an electron then it acquires a negative charge whereas when an atom loses an electron then it acquires a positive charge.
Atomic number of lithium is 3 and it loses one electron in order to attain stability. Thus, lithium ion has +1 charge.
Atomic number of calcium is 20 with electronic distribution as 2, 8, 2 and it loses two electrons in order to attain stability. Thus, calcium ion has +2 charge.
Atomic number of aluminium is 13 and it loses 3 electrons in order to attain stability. Thus, aluminium ion has +3 charge.
Atomic number of fluorine is 9 and it needs one electron in order to attain stability. Thus, fluorine ion has a charge of -1.
Atomic number of oxygen is 8 with electronic distribution as 2, 6 and in order to attain stability oxygen atom gains two electrons. Thus, oxygen ion has -2 charge.
