Naming CompoundsNaming Compounds

What's in a name? That which we call a roseBy any other name would smell as sweet."

- William Shakespeare, Romeo and Juliet (II, ii)

Prior to the 1700s, there was no systematic method of naming compounds. Substances were named in variety of ways, such as the use of compounds, the property of the compound, or the source of the substance. These names give little, if any, information about the composition of the compound.

Common Name: Quick lime/ Lime

IUPAC Name: Calcium Oxide

Chemical Formula: CaO

Use or property: Neutralizing acidified lakes

Common Name: Baking Soda

IUPAC Name: Sodium bicarbonate

Chemical Formula: NaHCO3

Use or property: Making baked goods rise

Common Name: Laughing gas

IUPAC Name: Dinitrogen monoxide

Chemical Formula: N2O

Use or property: Used in dentistry as

anaesthetic

Common Name: Table salt

IUPAC Name:  Sodium Chloride

Chemical Formula: NaCl

Use or property: Enhancing flavour

Common Name: Quartz sand

IUPAC Name: Silicon dioxide

Chemical Formula: SiO2

Use or property: manufacturing glass

• Valence electrons are the number of electrons in the outer energy level of an atom.

• “Valence” describes the number of electrons gained, lost or shared to achieve stability.

• For first 20 elements valence starts at 1 (alkali metals), climbs to 4 (group 4) and falls back to 1 (halogens)

• By knowing the valence of elements you can determine the formula of compounds

• E.g. what compound would form from C + S?Step 1 - write valences:

Step 2 – balance valences by adding atoms: Step 3 – write # of each atom as a subscript

Background: valences and formulas

C S4 2

C S4 2 2

CS2

a) Al,Br b) K,S c) Zn,O d) Mg,N e) C,Cl f) Na,O

AlBr3 K2S ZnO Mg3N2 CCl4 Na2O

Al Br

3 1

1

1

AlBr3

K S

1 2

1

K2S

Zn O

2 2

ZnO

Mg N

2 3

2 3

2

Mg3N2

C Cl

4 1

1

1

1

CCl4

Na O

1 2

1

Na2O

Ionic compoundsRules for naming

• Names end in -ide. Example: sodium chloride• 1. Write metal name first then non metal• 2. Change the ending of the non metal to “ide”• 3. Do not capitalized unless starting a

sentence

Give formulae & name: Ca + I, O + Mg, Na + S= Ca2I1 = CaI2 = calcium iodide= Mg2O2 = MgO = magnesium oxide= Na1S2 = Na2S = sodium sulfide

Multiple Valence

• Some metals have more than one valence.

• For these metals, you can use the Latin or IUPAC method

• Latin is older (not useful for some compounds)

• IUPAC is more commonly used

Latin naming• As before, the metal name if written first and

the non metal ends in -ide• The metal is named with it’s Latin or English

root and ends in “–ic” or “–ous” to denote valence

• E.g. Cu1 is cuprous, E.g. Cu2 is cupric• Lower = ous, Higher = ic• Give formulas and Latin names for:

Cu2 + Cl = Cu2Cl1 = CuCl2 = cupric chlorideCu1 + Cl = Cu1Cl1 = CuCl = cuprous chloride

Element (valence)

English name

Latin Name Higher valence

Lower valence

Metals that have and use latin names Cu (1,2) Copper Cuprum Cupric Cuprous Fe (2,3) Iron Ferrum Ferric Ferrous Pb (2,4) Lead Plumbum Plumbic Plumbous Sn (2,4) Tin Stannum Stannic Stannous

Metals that do not have latin names Co (2,3) Cobalt - Cobaltic Cobaltous Cr (2,3) Chromium - Chromic Chromous Mn (2,3) Manganese - Manganic Manganous

Metals that have latin names but use english root Hg (1,2) Mercury Hydrargyrum Mercuric Mercurous

High with the “i” Low with the “o”

Name the following:

• FeCl2

– Fe -> +2

– Cl -> -1

• CuO– Cu -> +2

– O -> -2

–Ferrous chloride - Cupric oxide

• Metal comes first, ending of non metal is “ide”• The valence of the metal is indicated in

brackets using roman numerals• E.g. Cu1 is copper(I), Cu2 is copper(II)• Numbers refer to valences not to #s of atoms• Try: Cu2+Cl, Zn2 + Cl, Co2+Cl, Hg+S (do both)

Cu2+Cl = Cu2Cl1 = CuCl2 = copper(II) chlorideZn2+Cl = Zn2Cl1 = ZnCl2 = zinc chlorideCo2+Cl = Co2Cl1 = CoCl2 = cobalt(II) chlorideHg+S = Hg1S2 = Hg2S = mercury(I) sulfideHg+S = Hg2S2 = HgS = mercury(II) sulfide

IUPAC naming

• Groups of atoms can also have valences• “Polyatomic ions” are groups of atoms that interact as

a single unit. • E.g. OH1, (SO4)2. Ba3(PO4)2 =

Compounds containing polyatomic ions• So far we have given valences to single atoms

Li + O Li1O2 Li2O

barium phosphate

• Naming compounds with polyatomic ions is similar to naming other ionic compounds

• Put the metal name first, then the name of the polyatomic second.

• You should note that compounds with polyatomic ions have names ending in -ate or -ite not -ide

• Name: Ca(OH)2, CuSO4, NH4NO3, Co2(CO3)3

- calcium hydroxide

- copper(II) sulfate

- ammonium nitrate

- cobalt(III) carbonate

Ca(OH)2

CuSO4

NH4NO3

Co2(CO3)3

Compounds containing polyatomic ions

Naming covalent compounds• -ide ending, each element has “prefix”1 mono

2 di

3 tri

4 tetra

5 penta

6 hexa

7 hepta

8 octa

9 nona

10 deca

• prefix refers to # of atoms - not valenceN2O4 = dinitrogen tetroxide

• Exception: drop mono for first elementCO2 = carbon dioxide

• The first vowel is often dropped to avoid the combination of “ao” or “oo”.

CO = carbon monoxide

(monooxide)SO2= sulfur dioxide (doxide)

• Name: CCl4, P2O3, IF7

P4O10= tetraphosphorus decoxide

Write and name the following covalent compounds (IUPAC)

carbon tetrachloride

diphosporus trioxide

iodine heptafluoride

CCl4

P2O3

IF7

Write the formulas for the following covalent compounds

(IUPAC)

dicarbon tetrasulfide

pentaphosphous dioxide

iodine octafluoride

C2Cl4

P5O2

IF8