Chemical can occur in two ways.

In ionic bonding an is removed from a [?] atom to give a metal ion which has a charge. The electron is transferred to the non metal atom which turns it into a ion. The of opposite charges hold the two ions together. Ionic compounds can form [?] structures, which we see as crystals.

Covalent compounds electrons. This enables the atoms in the compound to achieve the gas structure, which is very .