CHEMICAL NOMENCLATURE

Unit 05

Key Vocabulary

IUPAC - International Union of Pure and Applied Chemistry Responsible for chemical naming worldwide Rules for naming and writing compounds

Law of Definite Proportions – states that in samples of any chemical compound, the masses of the elements are always in the same proportions.

Chemical Formula - Symbols for its constituent elements are used; also shows number of atoms present in smallest representative unit of the substance.

Key Vocabulary

Oxidation Number – A measure of the charge of an atom if the electrons shared in bonding were held only by the more electronegative atom.

For example, in water (H2O), oxygen is more electronegative than hydrogen. This would give oxygen all the electrons and an oxidation number of -2 and each hydrogen an oxidation number of +1.

For simple atoms or ions, the oxidation number is equal to the ionic charge.

For a neutral element like Helium (He), the oxidation number is 0.

Key Vocabulary

Acid – compound that produces hydrogen ions (H+) in solution.

Base – compound that produces hydroxide ions (OH-) in solution.

Monatomic ion – a single atom with a + or – charge as a result of losing or gaining valence electrons. Examples: Na + Al 3+ P 3- Br

1-

Polyatomic ion – a tightly bound group of atoms that behaves as a unit and carries a charge. Examples: NH4

+ NO3- OH - SO4

2-

Transition Metals

Many of the cations of transition metals have more than one common ionic charge. Examples - cations of Iron: Fe 2+ and Fe 3+

This is also true for tin (Sn) and lead(Pb), the two metals in group 4A.

Use the stock system to name theseStock system – as part of the name of the

element, a Roman numeral in parentheses indicates the value of the charge. Example: Fe 2+ = Iron (II) and Fe 3+ = Iron (III) See page 144 in textbook, table 6.3 for more examples

Naming Simple Ionic Compounds

Ionic Compound = cation + anion

1. write the name of the cation (metal) If transition metal, useRoman numeral in parentheses

• Example: Iron(II)

2. write the anion(nonmetal)—change ending to –ide

Ex. NaCl cation = Sodiumanion = Chlorine

Name = Sodium chloride

Practice

CaI2 Calcium iodide

LiF Lithium fluoride

MgOMagnesium oxide

BeF2 Beryllium fluoride

FeCl2 Iron (II) chloride

Naming Ionic Compounds with Polyatomics

Polyatomic ion review 1. write the name of the cation (metal)

If transition metal, may need Roman numeral in parentheses

2. write the polyatomic ion— see common ones on your STAAR reference materials.

Special note: NH4+ is the only positive polyatomic

ion

See pp. 146-147 in textbook, table 6.4

Practice

Na2SO4 Sodium sulfate

CaCO3 Calcium carbonate

Li3PO3 Lithium phosphite

NH4Cl Ammonium chloride

Writing Ionic Formulas

Criss Cross Method 1. write chemical symbol for each element or

polyatomic

2. find the charge for each element or polyatomic (Transition metal—look at the roman numeral)

3. criss cross the charges to the opposite subscript

Notes: if charges can be reduced, do so before crossing down Use parentheses for polyatomics

Practice

Lithium fluoride LiF

Calcium sulfide CaS

Iron (III) chloride FeCl3

Potassium nitride K3N

Practice with polyatomics

Ammonium chloride NH4Cl

Sodium sulfate Na2SO4

Magnesium carbonate MgCO3

Naming Covalent Compounds

Covalent compound review

No charges

Share electrons

2 or more nonmetals

Examples: CO2, H2O, SF2

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Use prefixes to designate the subscriptPrefix Number

Mono 1

Di 2

Tri 3

Tetra 4

Penta 5

Hexa 6

Hepta 7

Octa 8

Nona 9

Deca 10

CO2

Carbon dioxide

Notes: the second element still takes the –ide ending Do not use mono for the first element

Practice

S2O4 Disulfur tetroxide

FCl3 Fluorine trichloride

N2O Dinitrogen monoxide

NO2 Nitrogen dioxide

Writing covalent formulas

Write the element symbol and add the prefix as subscript DO NOT CRISS CROSS …PREFIX STAYS WITH

ORIGINAL ELEMENT

Sulfur trioxide

Dinitrogen tetrafluoride

Hexasulfur pentaiodide