Assertion: Sulphates are polyatomic ions. Reason: The sulphate ion consist of one sulphur atom and 4 oxygen atom and carries an overall chare of "-2"

The assertion and the reason are both correct.

Sulphates are indeed polyatomic ions. A polyatomic ion is a charged particle which has two or more atoms held together by covalent bonds.

The sulphate ion is a perfect example of a polyatomic ion. It consists of one sulphur atom and four oxygen atoms, held together by covalent bonds. This ion carries an overall charge of -2. This is because the sulphur atom has 6 valence electrons and each oxygen atom has 6 valence electrons. When they combine, they form a stable ion with a full outer shell of electrons, but with an overall charge of -2 due to the extra electrons from the oxygen atoms.

So, the reason correctly explains why the assertion is true.