Ionic and Covalent Bonding Chapter 8/9

Chemical Formula Indicates the composition of a compound and the # of atoms in one molecule of an element Molecule – smallest particle of a substance that retains the composition and properties of that substance

Two Types of Molecules Monatomic Molecule – each molecule consists of a single atom –Ex: Ne, Ar and Ca Diatomic Molecule – each molecule contains 2 atoms - there are seven diatomic molecules - H 2, O 2, N 2, Cl 2, F 2, Br 2, I 2

Major Classes of Compounds Ionic Compounds – metal and a nonmetal bonded together Molecular Compounds – two or more nonmetals bonded together

Examples CaCl 2 - SO 2 – BaO – CCl 4 -

Atomic Structure ChargeSymbolMassLocation Proton Electron Neutron

Atomic Structure (cont’d) Atomic Number – Whole number on the periodic table - tells us the number of p + - tells us the number of e - in the neutral state Ex: C has _________ p + and e -

Atomic Structure (cont’d) Atomic Mass - the average mass of an atom - tells us the number of p t and n 0 together Therefore: # of neutrons = atomic mass – atomic number

Ionic Substances 1) A metal combines with a nonmetal 2) Electrons are transferred from the metal to the nonmetal 3)Elements no longer have a net charge of zero 4) Ions – (charged particles) are formed

Ionic Substances An element in an uncombined state has equal numbers of protons and electrons. Ex: Na11 p + Cl 17 p + 11 e - 17 e -0 charge

Lose Electron 1) Typically metals 2) Atom now has more p + than e - 3) An overall + charge 4) “Cation”

Gain Electron 1) Typically a nonmetal 2) Atom now has more e - than p + 3) An overall – charge 4) “anion”

Na + Cl  NaCl 1) each Na atom loses one e- – Na now has 11 p + and 10 e -  net charge +1 2) each Cl atom gains one e- - Cl now has 17 p + and 18 e -  net charge -1 *** the attraction between the + ion and the – ion is what allows the bond to form

Group #Elemente - config.Dot Diagram # of valence e - Gain or lose e - ? How many ? Charge of the ion

Predicting Formulas of Ionic Compounds The total net charge in an Ionic Compound MUST be ZERO Ex: Mg and F

Rules for Writing Formulas of Ionic Compounds 1)Write the symbols for the two elements Ex: Cation (Metal) always comes first 2) Determine the charge of each element 3) Determine the subscripts of each element Remember – the net charge must equal zero

Polyatomic Ions Groups of atoms of more than one element that carry a charge –Act as a single ion –Do not usually break up during a chemical rxn –Sulfate – SO 4 -2

List of Polyatomic Ions The sooner you learn them – the better!!!!! The formula of the ion is placed in parentheses and the subscript is placed outside the parentheses ex: Al +3 and SO 4 -2 Al 2 (SO 4 ) 3

Write the correct formulas for: Ba and Cl Li and S Sr and PO 4 -3 NH 4 +1 and S Al and S

Naming Ionic Compounds Binary Compounds – compounds made up of two elements - name of cation stays the same - name of anion – ending changes to –ide Ex: NaCl – sodium chloride

Naming Ionic Compounds (cont’d) Ternary Compounds – compounds made up of three or more elements - usually include a polyatomic ion - both ion names stay the same Ex: MgSO 4 - magnesium sulfate ** Exception – when NH 4 +1 bonds with a single element (ex: NH 4 +1 and O) the ending changes to -ide

Metals with more than 1 charge Copper+ 1 and +2 Lead+2 and +4 Iron +2 and +3 Tin +2 and +4

Stock System CuCl 2 vs. CuCl Both compounds CAN NOT be named Copper Chloride – we need some way of distinguishing between the two

Stock System Name of metal is followed by a Roman Numeral which indicates the charge of the cation *** look at previous example

Traditional System ● Uses suffixes at the end of the metals Latin root ● Smaller of the two ions receives suffix of – ous ● Larger of the two ions receives suffix of -ic

Traditional System Fe +2 ferrousPb +2 plumbous Fe +3 ferricPb +4 plumbic Cu +1 cuprousSn +2 Stannous Cu +2 cupricSn +4 Stannic

Formulas of Molecular Compounds Molecular Compounds – made up of molecules rather than ions –2 or more nonmetals bonded through the sharing of electrons

Oxidation # Apparent charge of an atom as it attracts or repels e - from another atom Oxygen typically has a -2 oxidation #

Example N 2 Onitrogen (II) oxideN = +1 NOnitrogen ( ) oxideN = N 2 O 3 nitrogen ( ) oxideN = NO 2 nitrogen ( ) oxideN = N 2 O 5 nitrogen ( ) oxideN =

Traditional System Uses prefixes to indicate subscripts on each atom SubscriptPrefix** Mono is never used with the 1Mono1 st element in the name of the 2dicompound (ex: CO and CO 2 ) 3tri 4tetra 5penta 6hexa 7hepta 8octa