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NOMENCLATURE / Oxidation Numbers

V. NOMENCLATURE

A. Oxidation Numbers (Oxidation States)

The ox. num. of an atom indicates the number of electrons it has lost or gained, either fully or partially.

1. Rules of the game:

a) In a simple ionic compound the ox. st. (ox. num.) of an atom is the same as its charge.

Example(1): MgS

Example(2): Na2O

b) The sum of the ox. num.'s in a neutral compound = zero.

Example(3): Al2O3

Example(4): FeCl3

c) In a covalent compound the ox. st. of an atom indicates the number of electrons partially lost or gained.

Example(5): From its dot formula, determine the oxidation state of each atom in HF

Example(6): From its dot formula, determine the oxidation state of each atom in H2O

Example(7): From its dot formula, determine the oxidation state of each atom in OF2

Example(8): From its dot formula, determine the oxidation state of each atom in CO2

d) The ox. st. of any element is zero.

Example(9): He

Example(10): Cl2

e) The sum of the ox. states in a polyatomic ion = its charge.

We will come back to this after we do “Predictable atoms” below

2. Predictable atoms in a compound

a) Group VII: F will always be -1 when it is in a compound.

Cl, Br, and I will be -1 if the atom is the most EN in the compound.

Example(11): NaF

Example(12): HF

Example(13): ClF

Example(14): BrCl

Example(15): HBr

b) Group VI: Oxygen will be -2 in a compound, except when with F or in a peroxide.

S, Se and Te will be -2 if the atom is the most EN in the compound.

Example(16): Na2O

Example(17): Cl2O

Example(18): OF2

Example(19): H2O2 (hydrogen peroxide)

Example(20): What is the ox. st. of sulfur in each of the following:

Na2SH2SS2SCl2SO2SO3

Example(21): What is the highest ox st S can obtain? Why?

Example(22): What is the lowest ox st S can obtain? Why?

c) Group V: N and P will be -3 if the atom is the most EN in the compound.

d) Group I Metals: - will always be +1 in a compound.

e) Group II: atoms will always be +2 in a compound.

f) H is +1 when bonded with something more EN than itself.

(Assume H has the lowest EN of the nonmetals.)

H is -1 when with something less EN than itself.

Example(23): HI

Example(24): NaH

Back to rule 1e) The sum of the ox. states in a polyatomic ion = its charge.

Example(25): What is the ox. st. of sulfur in MgSO4

Example(26): What is the ox. st. of sulfur in SO4-2

Example(27): What is the ox. st. of phosphorus in PO4-3

Example(28): What is the ox. st. of each Cr in Cr2O7-2

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NOMENCLATURE / Ionic Compounds

B. Nomenclature of Ionic Compounds

1. Simple Ionic Compounds

a) Positive ox. st. atom is written first in the formula.

(This is true for all nomenclature, with the exception of organic compounds and a few historically named compounds.)

b) Pos. ox. st. atom(s): ordinary elemental name.

c) Neg. ox. st. atom(s): root name + IDE ending.

Example(1): Name NaCl

Example(2): Name CaBr2

Example(3): Name Al2S3

Example(4): What is the formula of lithium nitride?

2. Compounds With A Metal That Can Display More Than One Ox. St.

a) New Nomenclature System: named like simple ionic, except a Roman numeral is used to indicate the ox. st. of each metal atom. All of the ions that you are required to know are on page 62.

Example(5): Name FeCl2 and FeCl3

Example(6): Name CuO and Cu2O

Example(7): Name SnS2

Example(8): What is the formula of mercury (II) nitride?

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NOMENCLATURE / Ionic Compounds

b) Old System: metal is named with its Latin root name + IC or OUS ending.

IC ending for the higher ox.st., OUS ending for the lower. All of the ions that you are required to know are on page 62.

Example(9): Name FeCl2 and FeCl3

Example(10): Name CuO and Cu2O

Example(11): What is the formula of stannic fluoride?

3. Polyatomic Ions

Some polyatomic ions follow a systematic method of nomenclature (most of the oxygen containing ions, see the rules below), other do not follow a system. All of the ions that you are required to know are on page 62.

a) Root name of the non-oxygen atom plus the ending ATE or ITE . The ATE and ITE endings indicate a polyatomic ion containing oxygen.

b) When there are 2 ions possible between an the element and oxygen use :

ATE for the one with more oxygen, ITE for the one with less oxygen

Example(12): Name SO4-2and SO3-2

Example(13): Name NO3-1and NO2-1

c) If there is only one ion, the ATE ending is used.

Example(14): Name PO4-3

Example(15): Name CO3-2

d) More than two ions

Example(16): Name the following:

ClO4-1

ClO3-1

ClO2-1

ClO-1

d) Polyatomic ions combined with one hydrogen ion

When we study acid-base theory you will see where these ions come from.

In the new system H is named as hydrogen since it has a positive ox. st.

In the old system the presence of hydrogen is indicated with “bi”.

Example(17): Name HCO3-1

Example(18): Name HSO4-1

4. Putting it altogether

Example(19): Name Na2SO3

Example(20): Name Al(HCO3)3

Example(21): Name Fe(NO3)2

Example(22): What is the formula of calcium hydrogensulfate?

Example(23): What is the formula of mercury(II) phosphate?

Example(24): What is the formula of ferric sulfate?

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NOMENCLATURE / Ionic Compounds

You should learn the names, formulas, and charges/oxidation states of the following common ions.

H+1hydrogenH-1hydride

Li+1lithiumF-1fluoride

Na+1sodiumCl-1chloride

K+1potassiumBr-1bromide

Mg+2MagnesiumI-1iodide

Ca+2calciumO-2oxide

Sr+2strontiumS-2sulfide

Ba+2bariumN-3nitride

Al+3aluminumP-3phosphide

Ag+1silverNO3-1nitrate

Zn+2zincNO2-1nitrite

Fe+2iron(II), [ferrous]SO4-2sulfateHSO4-1hydrogen sulfate

[bisulfate]

Fe+3iron(III), [ferric]SO3-2sulfiteHSO3-1hydrogen sulfite

[bisulfite]

Cu+1copper(I), [cuprous]ClO4-1perchlorate

Cu+2copper(II), [cupric]ClO3-1chlorate

Hg+1mercury(I), [mercurous]ClO2-1chlorite

Hg+2mercury(II), [mercuric]ClO-1hypochlorite

Sn+2tin(II), [stannous]CO3-2carbonateHCO3-1hydrogen carbonate

[bicarbonate]

Sn+4tin(IV), [stannic] PO4-3phosphate

H3O+1hydroniumOH-1hydroxide

NH4+1ammoniumCN-1cyanide

C2H3O2-1 acetate

MnO4-1 permanganate

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NOMENCLATURE / Covalent Compounds

C. Nomenclature of Simple Covalent

Simple covalent compounds are named like simple ions except when there is more than one atom of any type, a prefix is used to indicate the number.

Number Prefix

2di

3tri

4tetra

5penta

6hexa

Example(1): Name CO2

Example(2): Name SCl4

Example(3): Name H2O

Example(4): What is the formula of dinitrogen trioxide?

Example(5): What is the formula of carbon monoxide?