Electrons and Compounds

Electrons and Compounds

1. Electron shell rulles

   • Always occupy shells
   • Lowest energy levels are filled first (shell closest to the nucleus)
   • Only a certain number of electrons are allowed in each shell - 2,8,8
   • Full outer shells means they're unreactive
   • In most atoms if they're not full this makes the atom want to react to fill it

2. Compounds

   • When different elements react, atoms form chemical bonds with other atoms to form compounds
     • Properties are totally different from the original elements
   • Making bonds involves atoms giving away, taking or sharing electrons. Only electrons are involved
   • A compound which is formed from a metal and a non-metal consists of ions
     • Metal atoms lost electrons to form positive ions and non-metals gain electrons to form negative ions
       • Opposite charges of the ions mean they're strongly attracted. This is IONIC bonding
   • Formed from non-metals consists of molecules. Each atom shares an electron with another atom. This is COVALENT bonding
   • Can be small molecules like water or giant lattices like sodium chloride