chapter 6 chemical nomenclature

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Mark S. CracoliceEdward I. Peters

Mark S. Cracolice • The University of Montana

Chapter 6Chemical Nomenclature

Metals, Nonmetals and MetalloidsThe stair-step line in the periodic table separates metals from

nonmetals. Elements bordering this line are metalloids

Formulas of Elements

For most elements, the smallest independent particle is an atom.The formula of the element is the elemental symbol.

Element FormulaHelium HeLithium Li

Formulas of ElementsSeven elements form stable diatomic molecules

Compounds of Two NonmetalsBinary Molecular Compound

A compound formed by two nonmetalsor a metalloid and a nonmetal.

Compounds of Two NonmetalsNaming Binary Molecular Compounds

The first word is the name of the first element. A prefix is used to indicate the number of atoms.

The second word is the name of the second element, changed to end in –ide.A prefix is used to indicate the number of atoms.

Compounds of Two NonmetalsNumber prefixes used in chemical names

Number Prefix Number Prefix 1 mono- 6 hexa- 2 di- 7 hepta- 3 tri- 8 octa- 4 tetra- 9 nona- 5 penta- 10 deca-

Compounds of Two NonmetalsWrite the name of N2O5.

N = nitrogen; 2 = di

The first word is dinitrogen

O = oxygen, Change oxygen to end in -ide: oxide; 5 = penta

The second word is pentoxide (the letter a in prefixes is omitted if the resulting word sounds better)

dinitrogen pentoxide

Compounds of Two NonmetalsWrite the formula of nitrogen trifluoride.

No prefix on the first word, so mono- is implied = 1 atom.The symbol of nitrogen is N.Tri- prefix on the second word = 3 atoms.-fluoride is an “-ide modified” fluorine = F.

NF3

Compounds of Two NonmetalsTwo compounds are so common they are always called by their

traditional names:

H2O is water

NH3 is ammonia

Ions, Cations, AnionsIon

Charged particle formed when a neutral atomor molecule loses or gains electrons.

CationPositively charged ion.

AnionNegatively charged ion.

Ions formed by One ElementThe charge on a main-group (U.S. A group) ion

corresponds to its group number:

Group 1A 2A 3A 5A 6A 7A

Charge 1+ 2+ 3+ 3– 2– 1–

Ions Formed by One Element

Ions Formed by One ElementName of a monatomic cation

Name of element,followed by the word ion.

Name of a monatomic anionName of element changed to end in -ide,

followed by the word ion.

Ions Formed by One Element

What is the formula of a sodium ion?

Na+

Ions Formed by One ElementWhat are the name and formula of the ion formed from a chlorine

atom?

Cl–

Change the name chlorine to end in –ide.

Chloride ion

Ions Formed by One ElementMany transition elements (U.S. B groups) form multiple ions.

The charge is shown by a Roman numeral enclosed in parentheses.

Cr2+ is the chromium(II) ionCr3+ is the chromium(III) ion

Ions Formed by One ElementSome transition element ions always occur with only one charge

Zn2+ is zinc ionAg+ is silver ionNi2+ nickel ion

Special Case

Hg22+ is called mercury(I) ion.

Cations

Anions

Acids and Their AnionsAcid

Molecular compound that reacts with water to produce a hydrated hydrogen ion and an anion.

Ionization of hydrochloric acid HCl

H2O + HCl → H3O+ + Cl–

H3O+ is called hydronium ion.

Acids and Their AnionsThe Acids of Chlorine and Their Anions

# of O atoms Acid prefix Anion prefixCompared with and/or suffix and/or suffix-ic acid and -ate anion (Example) (Example)One more per- -ic per- -ateHClO4 (perchloric) (perchlorate)Same -ic -ateHClO3 (chloric) (chlorate)One fewer -ous -iteHClO2 (chlorous) (chlorite)Two fewer hypo- -ous hypo- -iteHClO (hypochlorous) (hypochlorite)No oxygen hydro- -ic -ideHCl (hydrochloric) (chloride)

Acids and Their AnionsThe names and formulas of following acids should be memorized

Acid Ionization Equation Ion NameChloric acid HClO3 H+ + ClO3

– Chlorate ionNitric acid HNO3 H+ + NO3

– Nitrate ionSulfuric acid H2SO4 2 H+ + SO4

2– Sulfate ionCarbonic acid H2CO3 2 H+ + CO3

2– Carbonate ionPhosphoric acidH3PO4 3 H+ + PO4

3– Phosphate ion

Acid AnionsStep-by-Step Acid Anion Nomenclature

H3PO4 phosphoric acid

H2PO4– dihydrogen phosphate ion

HPO42– hydrogen phosphate ion

PO43– phosphate ion

Acids and Their Anions

Formulas of Ionic CompoundsIonic Compound

A compound made up of ions.

The formula unit must have an equal number of positiveand negative charges.

Formulas of Ionic Compounds

Formula of the cation, followed by the formula of the anion. (omit the charges).

Subscripts are used to show the number of each ion in the formula unit.(sum of charges must equal to zero)

Omit the subscript if only one ion is needed.Enclose formula of the polyatomic ion in parentheses and

place the subscript after the closing parentheses.

Formulas of Ionic CompoundsWhat is the formula of magnesium chloride?

Magnesium is in Group 2A, so its ion is Mg2+.

Chlorine is in Group 7A, so its ion is Cl–.

Two 1– ions are needed to balance the 2+ ion.

MgCl2.

Formulas of Ionic CompoundsWhat is the formula of barium nitrate?

Barium cation is Ba2+

Nitrate anion is NO3–

Nitrate ion must be enclosed in parentheses

Ba(NO3)2

Other Acids and IonsMemorize the following common and important ions:

Hydroxide ion OH–

Ammonium ion NH4+

Names of Ionic CompoundsExample:Write the name of Zn(NO3)2.

Solution:Zinc ion has only one common charge, 2+, so the magnitude of

the charge is not included in its name: zinc ion.

NO3– comes from the memorized acid HNO3, nitric acid.

To name the ion, the -ic ending changes to -ate: nitrate ion.

Zinc nitrate

Names of Ionic CompoundsHow to Write the Name of an Ionic Compound

1. Write the name of the cation.2. Write the name of the anion.

Names of Ionic CompoundsWrite the name of CoCl2.

There is more than one common charge for cobalt ions.We will have to use the anion to determine this charge.

Chlorine is in Group 7A, so the charge on the ion is 1–: Cl–.The name of the anion is changed to end in -ide: chloride ion.

Two 1– ions require a 2+ ion to balance the charge: cobalt(II) ion.

Cobalt(II) chloride

HydratesHydrate

A solid compound that includes water molecules as part of its crystal structure.

HydratesWater of crystallization

Water molecules that are part ofthe crystal structure in a hydrate.

Anhydrous compoundAn ionic compound without water.

HydratesFormulas of Hydrated Compounds

Formula of ionic compound, followed by the number of water molecules, separated by a dot.

Example:Copper (II) sulfate pentahydrate

CuSO4 • 5 H2O

There are five water molecules forevery formula unit of copper (II) sulfate.

HydratesNames of Hydrated Compounds

Use the prefixes for naming binary molecular compoundsto indicate the number of water molecules associatedwith each formula unit of the anhydrous compound.

Example:MgSO4 • 7 H2O

Magnesium sulfate heptahydrate

HydratesExample:What is the formula of iron(III) sulfate nonahydrate?

Solution:Iron(III) ion is Fe3+.Sulfuric acid is H2SO4, so sulfate ion is SO4

2–.Nona- is the prefix for 9.-hydrate refers to water of hydration, H2O.2 × 3+ balances 3 × 2–.

Fe2(SO4)3 • 9 H2O

Homework

Homework for chapter 6:3, 5, 9, 13,15, 19, 21, 23, 25, 33, 35, 39, 41,43, 45, 47, 49Fill the tables 6-13, 6-14, 6-15 and 6-16