Bonding and Molecules

Why Bond? Most of the matter around you is in the form of compounds and mixtures. Compounds have different properties than the elements that make them up.

Valence Electrons The electrons located on the outermost electron shell are known as valence electrons. An atom is stable when its outer energy level is FULL.

Valence Electrons The maximum number of valence electrons is eight. (with the exception of H and He) These are the only electrons involved in bonding.

Octet Rule – “Magic 8” All atoms strive to have eight valence electrons. In order to achieve this octet (8), atoms will lose, gain or share electrons.

Valence Electrons can be identified using the Periodic Table.

Ions An atom that has gained or lost electrons and has a charge (+/-) A superscript is used to tell the charge (same as e- gained/lost). These are called oxidation numbers. Ex: Ca+2, Cl-1

Polyatomic Ions A molecule can have both covalent and ionic bonds in a compound containing a polyatomic ion.

Polyatomic Ions Ammonium - NH4+1 Nitrate - NO3-1 Sulfate - SO4-2 Phosphate - PO4-3

Chemical Bonds 1) Ionic Bond - forms when atoms gain or lose electrons Forms between metals and non-metals

2) Covalent Bond - forms when atoms share electrons Forms between two non-metal

Polar Molecules A covalent bond where electrons are not shared equally. Has oppositely charged ends that attract other charged molecules. Ex: H2O – the Hydrogen end is (+) and the Oxygen end is (-)