Chemical formula - combination of symbols that represent the composition of a compound

Shows elements present and number of atoms

subscripts

Represent the number of atoms of that element in the compound

No subscript is an “understood” 1

NaCl 1 Na 1 Cl H2SO4

2 H 1 S 4 O Ca(ClO3)2 ????? 1 Ca 2 Cl 6 O

Two types of compounds we will learn how to write formulas for

Ionic – transfer of electrons

Covalent – share electrons (called Molecular)

Molecular Compounds (covalent)

Representative unit – “molecule” (bonded covalently)

Type of elements – nonmetalsPhysical state – solid, liquid, gas

Solids – low melting point, brittle

Molecule – electrically neutral group of atoms that act as a unit

Naming binary molecular compounds

2 elements in the compound Both nonmetals!

2 naming systemsPrefix systemStock system (roman numerals)

Both systems are correct I’m sure you will prefer the prefix

system!

PREFIXES YOU MUST MEMORIZE!

Number of Prefix usedatoms 1 mono 2 di 3 tri 4 tetra 5 penta 6 hexa 7 hepta 8 octa 9 nona 10 deca

When 2 nonmetallic elements combineOften do so in more than one way

Example CO CO2

Problem with calling them both “carbon oxide”

CO2 – you exhale. It is normally present in the air you breathe

CO – hopefully is not in the air you breathe

In large amount R.I.P.Catalytic converter – cars

Converts CO to CO2

Prefix + first element nameFollowed by prefix + 2nd element

name with “ide” ending******only time you can not use a prefix is if the first element in the compound is a single atom

PCl3phosphorus trichloride

COCarbon monoxide (not monocarbon

monoxide!)

Don’t use “double vowels”Change if a “tongue twister”Monooxide monoxideDecaoxide decoxide

Trioxide – is fine

N2ODinitrogen monoxideSF6

Sulfur hexafluorideN2H4

Dinitrogen tetrahydride NO FACTORING ALLOWED!!!

P2O3

Diphosphorus trioxide

Name the following:

•CS2

•Carbon disulfide•Cl2O7

•Dichlorine heptoxide•P4O10

•Tetraphosphorus decoxide

•N2O5

•Dinitrogen pentoxide•CCl4

•Carbon tetrachloride

Write formulas for the following:•carbon tetrabromide•CBr4

•dinitrogen tetrahydride•N2H4

• boron trichloride• BCl3

• diphosphorus trioxide• P2O3

•A molecular compounds worksheet just for you!!

IONIC COMPOUNDS

•Four different types we will learn about

•Metal + nonmetal (binary ionic)

•Metal + polyatomic ion•Polyatomic ion + polyatomic ion

•Polyatomic ion + nonmetal

Ionic Charges•Monatomic ions – ions consisting of

only one atom•Charges can often be determined by

using the periodic table•Metallic elements – tend to lose

electrons to form cations•Group 1 – all 1+•Group 2 – all 2+

Nonmetals •Nonmetals tend to gain electrons when they bond with metals – form anions

Transition metals•Many have more than one common ionic charge

Are going to use roman numerals

I, II, III, IV, V

Oxidation number

• Indication of how many electrons it will gain or lose when it forms a bond

• Gains or loses electrons – forms an ion• Charged particle• Can be found for each element on the

periodic table• Refer to yours!!!

Some elements have more than 1 oxidation number – that means they can form more than one type of compound

When a single atom takes on a charge (by gaining or losing electrons) – it forms a

“monatomic ion”Ion made up of more than 1

atom – “polyatomic” ion

• Monatomic ions• Na+ Ca+2 Cl- O-2

• Polyatomic ions• CO3

-2 ClO3- OH-

Why would an atom want to form an ion?

Remember the “octet rule”

Wants a filled outer shell For most atoms, that is 8

Samples on board using electron dot notation

Na and ClCa and ClAl and ClCa and SK and N you do

Metal always written first – has positive oxidation number (written first)

Nonmetal written second – has negative oxidation number

Can use “criss-cross” method to arrive at correct formula.

Must remember to factor subscripts if possible!!

Magnesium oxide - MgO

Metal full name firstNonmetal name with “ide” endingNaCl sodium chlorideCaCl2 calcium chlorideLiF lithium fluorideAlBr3 aluminum bromide

Use Roman numerals to specify the oxidation number used

I, II, III, IV, V, VI, VII, VIIITransition metals characteristically

have multiple oxidation numbersONLY USE ROMAN NUMERALS IF THE

METAL HAS MORE THAN ONE OXIDATION NUMBER LISTED

Nonmetals may have more than one oxidation number, you just use the first number listed - NEGATIVE

Co, Ni, Cu, Fe, Mn

Always check before writing name for the compound

FeCl2 Iron(II) chlorideFeOFe2O3

calcium sulfideCaSstrontium bromideSrBr2

chromium(III) chlorideCrCl3

iron(II) oxideFeO

Fe2O3

Iron(III) oxideKIPotassium iodideCuOCopper(II) oxide

NiCl3Nickel(III) chlorideCrO3

Chromium(VI) oxide

2. Metal + polyatomic ion

Almost all polyatomic ions have a negative charge

2 you are responsible for have a positive charge NH4

+ and H3O+

Polyatomic ions travel as a unit Page 102 in text - list of polyatomic ions You will use the table I gave you

NEVER CHANGE THE SUBSCRIPTS IN A POLYATOMIC ION

THAT MEANS NEVER!!!!!!!

Can use same “criss-cross” method for determining the correct formula

Same rules apply – must factor the subscripts if you can (only the oxidation numbers that are used – NOT THE SUBSCRIPTS OF THE POLYATOMIC ION!!!!!!

At first, always put a parenthesis around the polyatomic ion

Only time the parenthesis can be dropped is if a “1” criss-crosses down or if the subscript factors to a “1”

Don’t forget to include a roman numeral in the name if the metal has multiple oxidation numbers!!!!!!

Metal name first (only use roman numeral if the metal has more than one oxidation number!!!)

Second is the name of the polyatomic ion – taken directly from the table!!

Don’t make up your own name!!!!!!!!

Representative unit = “formula unit”

Type of elements: Metal with nonmetal

Physical state: crystalline solid (hard)

High melting pointMost are soluble in H2O

Poor conductors of electricity in the solid stateBut good conductors when melted (molten) or dissolved in H2O (aq) (ions free to move)

Oxyacids – contain H, O and a third element (usually a nonmetal)

Acetic HCH3COO (acetate ion)

Nitric HNO3 (nitrate ion)

Nitrous HNO2 (nitrite ion)

Phosphoric H3PO4 (phosphate ion)

Sulfuric H2SO4 (sulfate ion)Sulfurous H2SO3 (sulfite ion)Carbonic H2CO3 (carbonate

ion)Hypochlorous HClO (hypochlorite

ion)Chlorous HClO2 (chlorite ion)Chloric HClO3 (chlorate ion)Perchloric HClO4 (perchlorate ion)

HF hydrofluoric acid

HCl hydrochloric acid HBr hydrobromic

acid HI hydroiodic acid