Formation of Negative Ions

1. Negative ions are formed among atoms of non-metal elements except group-18 elements.
2. Non-metal elements usually located in group 15, 16 and 17 in the periodic table and have 5, 6 or 7 valence electrons.
3. To achieve octet arrangement of electrons, their atoms will receive 3, 2 or 1 electron.
4. As a result, the electrons will out number the protons and hence negative ions formed.

Formation of Negative Ions of -1 Charge

(A fluorine atom receives one electron to form a fluoride ion with -1 charge)

Formation of Negative Ions of -2 Charge

(An oxygen atom receives two electrons to form a oxide ion with -2 charge)