Bonding

• Chemical bonds join atoms together to form molecules and compounds
• Chemical bonds form when atoms transfer or share electrons.
• Atoms transfer or share electrons with other atoms to get full outer shells
• There are 3 types of chemical bond: ionic, covalent and metallic.
• Ionic bonding joins metal and non-metal elements together.
• Covalent bonding joins non-metal elements together.
• Metallic bonding joins metal elements together.
• An ion is a charged atom or molecule
• Metal atoms can lose electrons from their outer shell.
• Positive ions have more protons than electrons.
• Non-metal atoms can gain electrons in their outer shell
• Negative ions have more electrons than protons.
• Atoms become ions in order to get a full outer shell of electrons; the 1st shell needs 2 electrons to be full and other shells need 8 electrons to be full.
• Ionic bonds form when electrons are transferred between atoms
• Electrons are transferred from metal atoms to non-metal atoms.
• The metal atoms lose electrons and the non-metal atoms gain electrons.
• Strong electrostatic forces hold the positive metal ion and negative non-metal ion together.
• Electrostatic forces are the attractive (and repulsive) forces between charged particles.
• The charge on an ion can be predicted from the periodic table
• Group 1 metals can lose their 1 outer electron to give 1+ (positive) ions.

  Group 2 metals lose their 2 outer electrons to give 2+ (positive) ions.

  Group 7 non-metals gain 1 outer electron to give 1- (negative)  ions.

  Group 6 non-metals gain 2 outer electrons to give 2- (negative) ions.

  • All of these ions have the electronic structure of a noble gas.

  (In other words, they have full outer shells of electrons.)
• Group 1 and 2 metals form ionic compounds with group 6 and 7 non-metals; their ions have opposite charges.
• Covalent bonds form when electrons are shared between atoms
• Covalent bonding joins non-metal elements together.

  It takes 2 electrons to make 1 covalent bond, one from each atom.

  This means that electrons are shared in pairs.
• Covalent bonds are very strong.
• Atoms only share electrons in their outer shells.
• In general, atoms form enough covalent bonds to fill up their outer shells.
• Having a full outer shell gives covalently bonded atoms the stable electronic structure of a noble gas.