Definitions Atom: smallest particle of an element that can exist and still have the properties of the element. Compound: A pure substance that can be broken down into two or more simpler pure substances by chemical means Molecule: group of two or more atoms that function as a unit because the atoms are tightly bound together

MOLECULAR COMPOUNDS All atoms are nonmetals Electrons are shared to form a bond IONIC COMPOUNDS Metal and a non metal Electrons are transferred to form cations and anions

Ionic vs molecular compounds

Molecular or Covalent bond Valence Electrons are shared

Homonuclear molecules (diatoms)and Heteronuclear molecules(polyatomic molecules)

Homonuclear molecules HONFIBrCl I never fly high over brown clouds

Molecule is the smallest particle of a compound capable of a stable, independent existence Phosphorus exists in a stable form of P-P-P-P Sulfur exists in a stable form of S-S-S-S-S-S-S-S What would be an easier way to write these symbols?

Compounds H 2 O # H ____, # O ___ C 6 H 12 O 6 # C______, # H _____, # O____ Mg(OH) 2 # Mg_____, # H_____, # O____ Ca 10 (PO 4 ) 6 (OH) 10 2 H 2 O #H in each molecule? _____________

Tell whether the following have ionic or covalent bonds CaCl 2 MgO CO 2 NH 4 Cl H 2 O HCl BaSO 4 KI K 2 O NaOH NaF NO 2 Na 2 CO 3 AlPO 4 CH 4 FeCl 3 SO 2 P 2 O 5 LiBr N 2 O 5

Naming Molecular compounds Binary compounds (not hydrocarbons) Two nonmetals Shared electrons Name ends in ide No ions formed Use Greek prefixes Mono*, di, tri, tetra, penta, hexa, hepta, octa, nona, deca

Naming molecular compounds formulaname P2O5P2O5 Dinitrogen trioxide NO Sulfur trioxide PI 3 SCl 6 Silicon dioxide

Lewis structures Atoms combine to form molecules so they will have lower energy Using only valence electrons try and give each atom a complete valence shell (complete octet except Hydrogen) Then try and give them the number of bonds they want : called covalency

Lewis structures group 1 simple structures FormulaLewis structure NH 3 H2OH2O N2H4N2H4 CH 4 O PF 3

Lewis structures group 2: polyatomic ions formulaLewis structure OH- NH 4 + NO 3 -

Lewis structures group 3: multiple bonds FormulaLewis structure H 2 CO HCN CO CO 2

Molecular geometry is not shown by Lewis structures

VSEPR Valence Shell Electron Pair Repulsion

Give the molecular geometry and bond angles of each structure