What is an octet? How do elements attain an octet?

(i) What is an octet? How do elements attain an octet?
(ii) Make a schematic atomic structure of magnesium and phosphorus.
[Given number of protons of magnesium =12 and that of phosphorus = 15 ]

(i) An outermost shell, which has eight electrons is said to possess an octet. Elements attain their octet by sharing, gaining or losing electrons. (1 +1)
(ii) Atomic structure of Mg

Atomic structure of P