What is matter? Write its si unit
Matter is anything that has mass and volume ( i.e. occupies space). Its SI unit is mole (mol).
Why is an atom electrically neutral?
An atom in its ground state contains equal number of electrons and protons. The magnitude of charge of both electrons and protons are equal. However, their nature of charges are opposite. Thus, they cancel each other's effect. As a result, an atom is electrically neutral.