Chemical bonding

• The world around us is made up of tiny units of matter called atoms. How these atoms stick together to form substances is called chemical bonding.
• Each clement has its own unique atom made up of a specific number of protons in its nucleus called the atomic number. Each atom also has the same number of electrons as it has protons.
• Valence Electrons 


  The valence electrons are the number of electrons in an outer shell of an atom that can participate in forming chemical bonds with other atoms.
• Ionic bonding 


  occurs when one element donates an electron (or electrons) to another so that both elements will have a full outer shell
• Covalent Bonding 


  electrons are shared between atoms rather than donated in order for the atoms of both elements to gain full outer shells. Electrons are always shared in pairs.
• Because noble gases have a naturally full outer shell they seldom react.
• Atoms in molecules are held together by the attraction between the nucleus and the shared electrons.