Chemical nomenclature(Naming compounds)

Chemistry Dept - FAST

Batterjee Medical CollegeObhur, KSA

At the end of these lectures you should be able to:1. Write symbols for elements and ions.

2. Name and write chemical formulae for ionic compounds

3. Name and writes chemical formulae of molecular compounds of two nonmetals.

4. Name a compound, given its chemical formula. Example: N2O4 is dinitrogentetroxide.

5. Write the chemical formula for a compound if you are given the name of that compound.

Example: manganese (IV) oxide is MnO2.

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Metal Cations• Metals with one possible

Charge (single charge):– metals whose ions can only

have one possible charge• Groups 1 Na+1 & gp 2

Mg+2, gp 3 Al+3, • Transition metals Ag+1,

Zn+2, Sc+3 – cation name = metal name

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Metal Cations

• Metals with more than one charge:

– Find charge by charge on anion.– cation name = metal name with Roman numbers charge in brackets

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Naming monatomic nonmetal anion• Find the charge from position on the Periodic

table.• To name anion, change ending on the element

name to –ide

Group 5= -3 Group 6= -2 Group 7 = -1

N3- = nitride O2- = oxide F- = fluoride

P3- = phosphide S2- = sulfide Cl- = chloride

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Write the formula of a compound made from aluminum ions and oxide ions

1. Write the symbol for the metal cation and its charge

2. Write the symbol for the nonmetal anion and its charge

3. Charge (without sign) becomes subscript for other ion.

4. Reduce subscripts to smallest whole number ratio

5. Check that the total charge of the cations cancels the total charge of the anions.

Al+3 Group 3

O2- Group 6

Al+3 O2-

Al2 O3

Al = (2) (+3) = +6∙O = (3) (-2) = -6∙

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Learning Check 1

What are the formulas for compounds made from the following ions?

•potassium ion with a nitride ion

•calcium ion with a bromide ion

•aluminum ion with a sulfide ion

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Solution 1

What are the formulas for compounds made from the following ions?

K+ with N3- K3N

Ca+2 with Br- CaBr2

Al+3 with S2- Al2S3

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Learning Check 2

What are the formulas for compounds made from the following ions?

1. copper(II) ion with a nitride ion

2. iron(III) ion with a bromide ion

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Solution 2

What are the formulas for compounds made from the following ions?

1. Cu2+ with N3- Cu3N2

2. Fe+3 with Br- FeBr3

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Rules for Ionic Compounds• made of cation and anion.• some have one or more nicknames that are

only learned by experience– NaCl = table salt, NaHCO3 = baking soda

• write systematic name by simply naming the ions– If cation is:

• metal with single charge = metal name [eg. Na+ (sodium)]• metal with more than one charge (Transition Metals) = metal

name(charge) [eg.Cu+ Copper (I), Cu2+ Copper(II)]• polyatomic ion = name of polyatomic ion [NH4

+ ammonium] – If anion is:

• nonmetal = part of nonmetal name + ide [eg. Flouride]• polyatomic ion = name of polyatomic ion [eg. Sulphate]

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Example 1: CsF

1. Identify cation and anionCs = Cs+ because it is Group 1

F = F- because it is Group 72. Name the cation

Cs+ = cesium3. Name the anion

F- = fluoride4. Write the cation name first, then the anion name

cesium fluoride

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Learning Check 3

Name the following compounds

1. KCl

2. MgBr2

3. Al2S3

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Solution 3

1. KCl potassium chloride

2. MgBr2 magnesium bromide

3. Al2S3 aluminum sulfide

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Example 2:CuF2

1. Identify cation and anionF = F- because it is Group 7

Cu = Cu2+ to balance the two (-) charges from 2 F-

2. Name the cationCu2+ = copper(II)

3. Name the anionF- = fluoride

4. Write the cation name first, then the anion namecopper(II) fluoride

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Learning Check 4

Name the following compounds

1. TiCl4

2. PbBr2

3. Fe2S3

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Solution 4

1. TiCl4 titanium(IV) chloride

2. PbBr2 lead(II) bromide

3. Fe2S3 iron(III) sulfide

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Compounds containing polyatomic Ions

• Polyatomic ions are single ions that contain more than one atom.

• Name and charge of polyatomic ion do not change.

• Name any ionic compound by naming cation first and then anion.

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Some Common Polyatomic IonsName Formulaacetate C2H3O2

–

carbonate CO32–

hydrogen carbonate( bicarbonate)

HCO3–

hydroxide OH–

nitrate NO3–

nitrite NO2–

chromate CrO42–

dichromate Cr2O72–

ammonium NH4+

Name Formulahypochlorite ClO–

chlorite ClO2–

chlorate ClO3–

perchlorate ClO4–

sulfate SO42–

sulfite SO32–

hydrogen sulfate(aka bisulfate)

HSO4–

hydrogen sulfite(aka bisulfite)

HSO3–

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1. Identify the ionsNa = Na+ because in Group 1SO4 = SO4

2- a polyatomic ion2. Name the cation

Na+ = sodium, metal with single charge3. Name the anion

SO42- = sulfate

4. Write the name of the cation followed by the name of the anion

sodium sulfate

Example 3:Na2SO4

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Example 4: Fe(NO3)3

1. Identify the ionsNO3 = NO3

- a polyatomic ionFe = Fe+3 to balance the charge of the 3 NO3

-1

2. Name the cationFe+3 = iron(III)

3. Name the anionNO3

- = nitrate4. Write the name of the cation followed by the

name of the anioniron(III) nitrate

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Learning Check 5

Name the following

1. NH4Cl

2. Ca(C2H3O2)2

3. Cu(NO3)2

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Solution 5

1. NH4Cl ammonium chloride

2. Ca(C2H3O2)2 calcium acetate

3. Cu(NO3)2 copper(II) nitrate

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Learning Check 6

What are the formulas for compounds made from the following ions?

1. aluminum ion with a sulfate ion

2. chromium(II) with hydrogen carbonate

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Solution 6

What are the formulas for compounds made from the following ions?

1. Al+3 with SO42- Al2(SO4)3

2. Cr+2 with HCO3─ Cr(HCO3)2

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Hydrates• hydrates are ionic compounds

containing a specific number of waters for each formula unit.

• water of hydration often “driven off” by heating.

• in formula, attached waters follow ∙– CoCl2∙6H2O

• -add hydrate after name of ionic compound– CoCl2 6H∙ 2O = cobalt(II) chloride hexa hydrate– CaSO4∙½H2O = calcium sulfate hemi hydrate

Prefix No. of Waters

hemi ½

mono 1

di 2

tri 3

tetra 4

penta 5

hexa 6

hepta 7

octa 8

Hydrate

CoCl2∙6H2O

AnhydrousCoCl2

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Learning Check 7

1. What is the formula of magnesium sulfate heptahydrate?

2. What is the name of NiCl2•6H2O?

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Solution 7

1. What is the formula of magnesium sulfate heptahydrate? MgSO47H2O

2. What is the name of NiCl2•6H2O? nickel(II) chloride hexahydrate

Naming of covalent compounds

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Writing names of binary molecular compounds of 2 nonmetals

1. Write name of first element in formula– element furthest left and down on the Periodic Table– use the full name of the element

2. Write name of the second element in the formula with an -ide suffix

– as if it were an anion, however, remember these compounds do not contain ions!

3. Use a prefix in front of each name to indicate the number of atoms

_ never use the prefix mono- on the first element

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Subscript - prefixes

• 1 = mono- – not used on first

nonmetal• 2 = di-• 3 = tri-• 4 = tetra-• 5 = penta-

• 6 = hexa-• 7 = hepta-• 8 = octa-• 9 = nona-• 10 = deca-

• drop last “a” if name begins with vowel

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Example 5: BF3

1. Name the first elementboron

2. Name the second element with an –idefluorine fluoride

3. Add a prefix to each name to indicate the subscript

monoboron, trifluoride4. Write the first element with prefix, then the

second element with prefix– Drop prefix mono from first element

boron trifluoride

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Learning Check 8

Name the following1. NO2

2. PCl5

3. I2F7

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Solution 8

1. NO2 nitrogen dioxide

2. PCl5 phosphorus pentachloride

3. I2F7 diiodine heptafluoride

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Example 6:dinitrogen pentoxide

• Identify the symbols of the elements

nitrogen = N

oxide = oxygen = O• Write the formula using prefix number for

subscript

di = 2, penta = 5

N2O5

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Learning Check 9

Write formulas for the following

1. dinitrogen tetroxide

2. sulfur hexafluoride

3. diarsenic trisulfide

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Solution 9

1. dinitrogen tetroxide N2O4

2. sulfur hexafluoride SF6

3. diarsenic trisulfide As2S3

covalent formulae Ionic formulae

H2O

CO2

NH3

H2

O2

N2

SO2

Water

Carbon dioxide

Ammonia

Hydrogen

Oxygen

Nitrogen

Sulphur dioxide

NaCl

CaCl2

MgO

HCl(aq)

H2SO4(aq)

HNO3(aq)

NaOH

Ca(OH)2

CaCO3

Al2O3

Fe2O3

Sodium chloride

Calcium chloride

Magnesium oxide

Hydrochloric acid

Sulphuric acid

Nitric acid

Sodium hydroxide

Calcium hydroxide

Calcium carbonate

Aluminium oxide

Iron (III)oxide