A compound consists of two or more atoms from different elements chemically joined together. There are two types of chemical bond:
- - covalent bonds
- - ionic bonds.
A covalent bond forms when two atoms share a pair of electrons. The atoms involved are non-metals such as carbon, oxygen and hydrogen. They join together to form molecules.
The animation shows a covalent bond being formed between a hydrogen atom and a chlorine atom to form a molecule of hydrogen chloride:
Atoms can lose or gain electrons in chemical reactions. When they do this they form charged particles called ions.
- hydrogen atoms and metal atoms can lose electrons to form positively charged ions.
- non-metal atoms can gain electrons to form negatively charged ions.
Ionic bonds are the forces of attraction between oppositely charged ions in a compound.