Writing Formulas and Naming Compounds

Atoms and molecules react with one another to become more stable. Atoms become more stable by either gaining/losing electrons so that they have 8 valence electrons (full outer energy level).

Na 1s2 2s2 2p6 3s1 1 valence electron

Cl 1s2 2s2 2p6 3s2 3p5 7 valence electrons

Sodium will lose 1 e- to get 8 valence electrons (a noble gas configuration). Chlorine will gain 1e- to get 8 valence e- (a noble gas configuration).

Na Na+1 + 1e-

Cl + 1e- Cl-1

Na+1 + Cl-1 NaCl

The Na+1 and Cl-1 ions have very different properties than the Na and Cl atoms.

Atoms form ions by gaining or losing electrons. The metals tend to lose electrons (positive ions), the nonmetals tend to gain electrons (negative ions).

The position of the element on the periodic table can help determine how many valence electrons the atom has, and what charge it will probably have when it becomes an ion.

Groups and Ion ChargesGroups and Ion Charges

GroupGroup Valence e-Valence e- Gain/Lose e-Gain/Lose e- Ion chargeIon charge

11 11 Lose 1Lose 1 +1+1

22 22 Lose 2Lose 2 +2+2

1313 33 Lose 3Lose 3 +3+3

1414 44 TweenerTweener +4/-4+4/-4

1515 55 Gain 3Gain 3 -3-3

1616 66 Gain 2Gain 2 -2-2

1717 77 Gain 1Gain 1 -1-1

1818 88 00 00

Ions are atoms with different numbers of protons and electrons. They are formed by either gaining or losing electrons.

If an atom loses electrons, it has more protons than electrons and becomes positively charged. This is called a cation, and usually happens to the metals.

If an atom gains electrons, it has more electrons than electrons and becomes negatively charged. This is called an anion, and usually happens to the nonmetals.

Monatomic Ions – an ion made up of only one type of atom (H+1, Ca+2, S-2, Cl-1, …)

Polyatomic Ions – an ion made up of two or more different types of atoms (NO3

-1, OH-1, SO4

-2, NH4+1, …)

The compound Na3PO4 is made up of 3 monatomic ions (Na+1) and 1 polyatomic ion (PO4

-3).

Ions are named differently than elements because they have different properties. In General

•Metals – the word ion is added after the name of the element. Na = sodium Na+1 = sodium ion

•Nonmetals – the ending of the element is dropped, and –ide is added.

Br = bromine Br-1 = bromide

O = oxygen O-2 = oxide

Ionic compounds are made from ions combining. The compound has no net charge, or is neutral, even though it is made up of both positive and negative ions.

Naming compounds and writing formulas is easy if you know the names, charges and formulas of all of the ions on the ion list. If you don’t know these, you will be guessing on all of your names or formulas.

Polyatomic IonsPolyatomic Ions

FormulaFormula NameName

NHNH44+1+1 AmmoniumAmmonium

NONO33-1-1 NitrateNitrate

ClOClO33-1-1 ChlorateChlorate

OHOH-1-1 HydroxideHydroxide

CC22HH33OO22-1-1 AcetateAcetate

SOSO44-2-2 SulfateSulfate

COCO33-2-2 CarbonateCarbonate

POPO44-3-3 PhosphatePhosphate

Elements with more than one Elements with more than one chargecharge

NameName SymbolSymbol NameName SymbolSymbol

Copper (I)Copper (I) CuCu+1+1 Copper (II)Copper (II) CuCu+2+2

Chromium (II)Chromium (II) CrCr+2+2 Chromium (III)Chromium (III) CrCr+3+3

Manganese (II)Manganese (II) MnMn+2+2 Manganese (III)Manganese (III) MnMn+3+3

Cobalt (II)Cobalt (II) CoCo+2+2 Cobalt (III)Cobalt (III) CoCo+3+3

Iron (II)Iron (II) FeFe+2+2 Iron (III)Iron (III) FeFe+3+3

Nickel (II)Nickel (II) NiNi+2+2 Nickel (III)Nickel (III) NiNi+3+3

Tin (II)Tin (II) SnSn+2+2 Tin (IV)Tin (IV) SnSn+4+4

Lead (II)Lead (II) PbPb+2+2 Lead (IV)Lead (IV) PbPb+4+4

Naming Ionic Compounds

Give the name of the positive ion, cation, including the roman numeral if appropriate followed by the name of the negative ion, anion.

•Names of the cation are the same as the name of the element.

•Names of monatomic anions usually end with -ide.

•Names of polyatomic anions usually end with –ate.

NaCl sodium chloride

LiNO3 lithium nitrate

CuCl copper (I) chloride

CuCl2 copper (II) chloride

Sr(ClO3)2 strontium chlorate

MgO magnesium oxide

CaSO4 calcium sulfate

FeBr3 iron (III) bromide

Writing correct ionic formulasWriting correct ionic formulas

Write the cation followed by the anionWrite the cation followed by the anion Cross the numerical charges to become Cross the numerical charges to become

the subscripts. Drop all +/- signsthe subscripts. Drop all +/- signs If the subscripts are 1, do not write the 1. If If the subscripts are 1, do not write the 1. If

the subscripts are multiples, reduce them.the subscripts are multiples, reduce them. If more than one polyatomic ion is needed, If more than one polyatomic ion is needed,

put ( ) around the polyatomic ion before put ( ) around the polyatomic ion before adding the subscript.adding the subscript.

Ionic Compounds

•Made up of positive and negative ions

•Made up of metals and nonmetals

•“Salts”

•Will conduct electricity when dissolved in water

•Electrons are transferred between atoms

•Opposites attract

•Positive ion always comes first

Covalent Compounds

•Made up of two or more nonmetals

•Electrons are shared between atoms

•Do not conduct electricity in water

•No ions are present

PrefixesPrefixes

PrefixPrefix MeaningMeaning PrefixPrefix MeaningMeaning

Mono-Mono- 11 Hexa-Hexa- 66

Di-Di- 22 Hepta-Hepta- 77

Tri-Tri- 33 Octa-Octa- 88

Tetra-Tetra- 44 Nona-Nona- 99

Penta-Penta- 55 Deca-Deca- 1010

Naming covalent compoundsNaming covalent compounds

Give the prefix telling how many of the first Give the prefix telling how many of the first element (except mono-), then give the element (except mono-), then give the name of the first element.name of the first element.

Give the prefix telling how many of the Give the prefix telling how many of the second element, then give the name of the second element, then give the name of the second element ending with –ide.second element ending with –ide.

PP22OO55 COCO COCO22 NN22OO44

PClPCl33 IClICl33 SiOSiO22 NN44ClCl77

Naming Acids: HX, HNaming Acids: HX, H22X, HX, H33XX

If the anion X ends in –ideIf the anion X ends in –ide hydro (name of anion, drop the ending) –ic acidhydro (name of anion, drop the ending) –ic acidHCl hydro chloric acid HBr hydrobromic acidHCl hydro chloric acid HBr hydrobromic acidHH22O hydro oxic acidO hydro oxic acid H H22S hydro sulfuric S hydro sulfuric

acidacid

If the anion X ends in –ateIf the anion X ends in –ate (name of the anion, drop the ending)-ic acid(name of the anion, drop the ending)-ic acidHNOHNO33 nitric acidnitric acid H H22SOSO44 sulfuric acid sulfuric acidHClOHClO33 chloric acidchloric acid HC HC22HH33OO22 acetic acid acetic acid

Names and formulas of common Names and formulas of common acidsacids

HH22SOSO44

HClHClHNOHNO33

HCHC22HH33OO22

HH33POPO44

Sulfuric AcidSulfuric AcidHydro chloric Hydro chloric

acidacidNitric acidNitric acidAcetic acidAcetic acidPhosphoric AcidPhosphoric Acid