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 orCovalent bond

ValenceElectrons areshared

Homonuclear molecules (diatoms)and Heteronuclear molecules(polyatomic

molecules)

Homonuclear molecules

HONFIBrClI 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

• H2O # H ____, # O ___

• C6H12O6 # C______, # H _____, # O____

• Mg(OH)2 # Mg_____, # H_____, # O____

• Ca10(PO4)6(OH)10

• 2 H2O #H in each molecule? _____________

Tell whether the following have ionic or covalent bonds

• CaCl2 MgO

• CO2 NH4Cl

• H2O HCl

• BaSO4 KI

• K2O NaOH

• NaF NO2

• Na2CO3 AlPO4

• CH4 FeCl3

• SO2 P2O5

• LiBr N2O5

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

formula nameP2O5

Dinitrogen trioxideNO

Sulfur trioxidePI3

SCl6

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 structuresgroup 1 simple structures

Formula Lewis structureNH3

H2O

N2H4

CH4O

PF3

Lewis structuresgroup 2: polyatomic ions

formula Lewis structure

OH-

NH4+

NO3-

Lewis structuresgroup 3: multiple bonds

Formula Lewis structure

H2CO

HCN

CO

CO2

Molecular geometryis not shown by Lewis structures

VSEPR

• Valence Shell Electron Pair Repulsion

Give the molecular geometry and bond angles of each structure