Stability Octet Rule –most atoms form bonds in order to have 8 valence e - –full outer energy level –like the Noble Gases! Ne  Stability is the driving force behind bond formation!

Stability Transferring e -  Sharing e -

Chemical Bonding The combining of elements to form new substances Valence # determines whether or not the atom will form chemical bonds Oxidation #

Ionic compounds Bonding that involves a transfer of electrons from one atom to another Na will give up its electron to Cl so Na is 1 + ion and Cl is a 1 - ion

Ionic compounds Strong attraction between opposite charges hold the atoms together in an ionic bond Ionization energy – the energy needed to remove electrons and form ions Electron affinity – the tendency of an atom to attract electrons

Arrangement of ions in ionic compounds Ions of opposite charges attract one another and ions of same charge repel one another Crystal lattice structure Anion Cation Responsible for physical properties of ionic compounds

Write the chemical formula for: Mg & S Li & F K & As In & Cl Sr & N Ge & P Ga & O Cs & S Ca & P Al & Br Ba & Se B & Bi MgS LiF K 3 As InCl 3 Sr 3 N 2 Ge 3 P 4 Ga 2 O 3 Ca 3 P 2 Cs 2 S AlBr 3 BaSe BBi

Covalent Compounds Electrons are shared instead of transferred By sharing electrons, both atoms fill up their outermost energy level Happens when neither atom loses electrons easily, but both atoms attract electrons Electron sharing can be represented by an electron-dot diagram (Lewis structure) Chemical symbol surrounded by dots representing the valence electrons

Electron dot diagrams

Draw the electron dot diagrams for: HCl NH 3 H 2 O Cl 2 O 2 N 2 CO 2 HClO 3 C 2 H 6 CH 4 S H 2 CO 3 SO 3 C 2 H 3 O 2

Polyatomic Ions A group of covalently bonded atoms that acts like a single atom when combining with other atoms Usually form ionic bonds with other atoms

Some Common Polyatomic Ions Ammonium Acetate Chlorate Hydrogen carbonate Hydroxide Nitrate Nitrite Carbonate Sulfate Sulfite phosphate NH 4 1+ C 2 H 3 O 2 1- ClO 3 1- HCO 3 1- OH 1- NO 3 1- NO 2 1- CO 3 2- SO 4 2- SO 3 2- PO 4 3-

Write the chemical formula for: Al & PO 4 Rb & SO 4 NH 4 & CO 3 Sr & OH K & NO 3 Sn & SO 3 Ga & SO 4 Be & OH Li & NO 2 Cr (I) & C 2 H 3 O 2 Cu (II) & PO 4 Ba & OH

PropertyIonic CompoundsCovalent Compounds Physical state at room temperature SolidsGases, liquids, or low melting pt. solids Electrical conductivity of water solution ConductorsNonconductors Water solubilityMany are solubleMost are not soluble Melting pointVery highMuch lower than ionic compounds Shape of a solid sample Crystalline with characteristic angles May be crystalline but lacking characteristic angles VolalityTend to have low odorTend to have high odor