Chapter 9Naming Ions

Monatomic Ions

Ionic compounds consists of a positive metal ion and a negative nonmetal ion combined in a proportion such that their charges add up to a net charge of zero.

NaCl – consists of one Na+ and one Cl-.

Monatomic ions Monatomic ions consists of a single atom with a positive or negative charge resulting from the loss or gain of one or more valence electrons.

Monatomic Ions - CationsCations tend to lose valence electrons. (1+ charge – lose 1 electron, 2+ charge – lose 2 electrons, etc. )

When the metals in Groups 1A, 2A, and 3A lose electrons, they form cations with positive charges equal to their group number.

The name of the cations of the Group 1A, 2A and 3A are the same as the name of the metal, followed by the word ion or cation.

Na+ is sodium ion, Ca2+ is calcium ion, Al3+ is aluminum ion.

Monatomic Ions - AnionsNonmetals tend to gain electrons for form anions, so the charge of a nonmetallic ion is negative.

The charge of any ion of a Group A nonmetal is determined by subtracting 9 from the group number.

Group 7A form anions with a 1- charge (7-8 = -1)

Anion names start with the stem of the element name and end in –ide.

Anion of fluorine is fluoride ion (F-), anion of chlorine is chloride ion (Cl-)

Ions of Transition MetalsMany of the transition metals (Group 1B – 8B) form more than one cation with different ionic charges.

Two methods are used to name these ions.

1.1.Stock System Stock System – a roman numeral in parentheses is placed after the name of the element to indicate the numerical value of the charge.

Fe2+ is iron(II) ions Fe3+ is iron(III) ion.

2.2.ClassicalClassical – name of the element is used to form the root name for the element.

Fe2+ is ferrous ion Fe3+ is ferric ions

Fe2+ iron(II) / ferrous

Fe3+ iron(III) / ferric

Hg1+ mercury(I) / mercurous

Hg2+ mercury(II) / mercuric

Mn2+ manganese(II)

Mn3+ manganese(III)

Mn4+ manganese(IV)

Ni2+ nickel(II) / nickelous

Ni3+ nickel(III) / nickelic

Pb2+ lead(II) /plumbous

Pb4+ lead(IV) / plumbic

Ag1+ silver

Cd2+ cadmium

Zn2+ zinc

Au1+ gold(I) / aurous

Au3+ gold(III) / auric

Co2+ cobalt(II) / cobaltous

Co3+ cobalt(III) /cobaltic

Cr2+ chromium(II) / chromous

Cr3+ chromium(III) /chromic

Cu1+ copper(I) / cuprous

Cu2+ copper(II) /cupric

Polyatomic IonsPolyatomic Ions Polyatomic Ions are composed of more than one atom.

Sulfate ions (SO42-) is composed of one sulfur atom and

four oxygen atoms.

Polyatomic ions are a tightly bound group of atoms that behave as a unit and carry a charge.

The names of most polyatomic anions end in –ite or –ate.

+1 CHARGE

ion name

NH4+ ammonium

H3O+ hydronium

Hg22+ mercury(I)

-1 CHARGE ion name

H2PO3- dihydrogen phosphite

H2PO4- dihydrogen phosphate

HCO3- hydrogen carbonate

HSO3- hydrogen sulfite

HSO4- hydrogen sulfate

NO2- nitrite

NO3- nitrate

OH- hydroxide

CH3COO- acetate

-1 CHARGE

ion name

CrO2- chromite

CN- cyanide

CNO- cyanate

CNS- thiocyanate

O2- superoxide

MnO4- permanganate

ClO- hypochlorite

ClO2- chlorite

ClO3- chlorate

ClO4- perchlorate

-1 CHARGE

ion name

BrO- hypobromite

BrO2- bromite

BrO3- bromate

BrO4- perbromate

IO- hypoiodite

IO2- iodite

IO3- iodate

IO4- periodate

AlO2- aluminate

N3- azide

-2 CHARGE

ion name

HPO32- hydrogen

phosphite

HPO42- hydrogen

phosphate

CO32- carbonate

SO32- sulfite

SO42- sulfate

S2O32- thiosulfate

SiO32- silicate

-2 CHARGE

ion name

C22- carbide

C2O42- oxalate

CrO42- chromate

Cr2O72- dichromate

C4H4O62- tartrate

MoO42- molybdate

O22- peroxide

S22- disulfide

-3 CHARGE -4 CHARGE

ion name ion name

PO33- phosphite P2O7

4- pyrophosphate

PO43- phosphate

PO23- hypophosphite

AsO33- arsenite

AsO43- arsenate

End of Section 9.1

Naming Binary Ionic Compounds

A binary compound binary compound is composed of two elements and can be either ionic or molecular (covalent)

To name any binary ionic compound, place the cation name first, followed by the anion name.

Cs2O is cesium oxide NaBr is sodium bromide

Cu2O is copper(I) oxide CuO is copper(II) oxide

Writing Formulas Binary Ionic Compounds

Write the symbol of the cation and then the anion. Add whatever subscripts are needed to balance the charges.

The positive charge of the cation must balance the negative charge of the anion so that the net ionic charge of the formula is zero.

K+ + Cl- KCl

Ca2+ + Br- CaBr2

Fe3+ + O2- Fe2O3

Use the crisscross method crisscross method – the numerical value of the charge of each ion is crossed over and becomes the subscript for the other ion.

Writing Formulas Polyatomic Ionic Compounds

An –ate or –ite ending on the name of a compound indicates that the compound contains a polyatomic anion that includes oxygen.

Write the symbol for the cation followed by the formula for the polyatomic ion and balance the charges.

Ca2+ + NO3- Ca(NO3)2

Sr2+ + SO32- SrSO3

Li+ + CO32- Li2CO3

Use the crisscross method – the numerical value of the charge of each ion (polyatomic too) is crossed over and becomes the subscript for the other ion.

Naming Polyatomic Ionic Compounds

First recognize that the compound contains a polyatomic ion.

State the cation first and then the anion

NaClO

sodium hypochlorite

(NH4)2C2O4

ammonium oxalate

Li2CO3

lithium carbonate

End of Section 9.2

Naming Molecular CompoundsBinary ionic compoundsBinary ionic compounds are composed of the ions of two elements, a metal and a nonmetal.

Binary molecular compoundsBinary molecular compounds are composed of two elements, two nonmetals and they are not ions.

Binary molecular compounds are composed of molecules, not ions, so ionic charges cannot be used to write formulas or to name them.

In addition, when two nonmetallic elements combine, the often do so in more than one way. (CO, CO2)

Prefixes in the names of binary molecular compounds help distinguish compounds containing different amounts of the same two elements.

Naming Molecular CompoundsThe prefix in the name of a binary molecular compound tells how many atoms of each element are present in each molecule of the compound.

Prefix Number

mono- 1

di- 2

tri- 3

tetra- 4

penta- 5

hexa- 6

hepta- 7

octa- 8

nona- 9

deca- 10

Naming Molecular CompoundsThe names of all binary molecular compounds end in –ide.

CO is carbon monoxide

CO2 is carbon dioxide

If just one atom of the first element is in the formula, omit the prefix mono-

•Name the elements in order listed in the formula

•Use prefixed to indicate the number of each kind of atom

•The suffix of the name of the second element is –ide.

N2O is dinitrogen monoxide

SF6 is sulfur hexafluoride.

Writing FormulasMolecular Compounds

Use the prefixes in the name to tell you the subscript of each element in the formula.

Then write the correct symbols for the two elements with the appropriate subscripts.

Silicon Carbide

SiC

Dinitrogen tetraoxide

N2O4

Diphosphorus trioxide

P2O3

End of Chapter 7End of Section 9.3

Naming Acids

AcidAcid is a compound that contains one or more hydrogen atoms and produces hydrogen ions (H+) when dissolved in water.

When naming acids, the acid consists of an anion combined with as many hydrogen ions s are needed to make the molecule electrically neutral.

The general chemical formulas of acids is HnX.

X is a monatomic or polyatomic anion

n is a subscript indication the number of hydrogen ions combined with the anion.

Naming Acids

Three rules are used to name acids. The name depends on the name of the anion and its suffix (-ide, -ite, -ic)

1.a. When the name of the anion ends in –ide, the acid name begins with the prefix hydro-.

b. The stem of the anion has the suffix –ic and is followed by the word acid.

H+ + Cl- HCl

Hydrogen ion chlorideide ion hydrohydrochloricic acid

H+ + S2- H2S

Hydrogen ion sulfideide ion hydrohydrosulfuricic acid

Naming Acids

Three rules are used to name acids. The name depends on the name of the anion and its suffix (-ide, -ite, -ic)

2.a. When the anion name ends in –ite, the acid name is the stem of the anion with the suffix –ous, followed by the word acid

H+ + SO32- H2SO3

Hydrogen ion sulfiteite ion sulfurousous acid

H+ + IO2- HIO2

Hydrogen ion ioditeite ion iodousous acid

Naming Acids

Three rules are used to name acids. The name depends on the name of the anion and its suffix (-ide, -ite, -ic)

3.a. When the anion name end in –ate, the acid name is the stem of the anion with the suffix –ic followed by the word acid.

H+ + NO3- HNO3

Hydrogen ion nitrateate ion nitricic acid

H+ + SO42- H2SO4

Hydrogen ion sulfateate ion sulfuric ic acid

Writing Formulas for Acids

Use the rules for writing the names of acids in reverse to write the formula for acids.

HydroHydrobromicic acidHydro indicates the bromideide ion

HBr

Phosphorousous acid-ous indicates the phosphiteite ion

H3PO3

Formic acid-ic and beginning with the anion name indicates the formateate ion

HCOOH

BasesA basebase is an ionic compound that produced hydroxide ions (OH-)when dissolved in water.

Bases are named the same way as other ionic compounds – the name of the cation is followed by the name of the anion.

NaOH is sodium hydroxide

To write the formulas for bases, write the symbol for the cation followed by the formula for the hydroxide ion. (balance the ionic charges jusat as you do for any ionic compound)

Aluminum hydroxide – Al3+ + OH- Al(OH)3

Ammonium hydroxide – NH4+ + OH- NH4OH

End of Chapter 7End of Section 9.4

Laws Governing Formulas & NamesLaw of Definite ProportionsLaw of Definite Proportions

A chemical formula tells you (by subscripts) the ratio of atoms of each element in the compound.

Ratios of atoms can also be expressed as ratios of masses.

100 g of MgS breaks down into 43.12g Mg and 56.88g of sulfur.

100g MgS 1 mol MgS 1 mol Mg 24.305g Mg = 43.12g Mg

56.4g MgS 1 mol MgS 1 mol Mg

100g MgS 1 mol MgS 1 mol S 32.06g S = 56.88g S 56.4g MgS 1 mol MgS 1 mol S

Laws Governing Formulas & Names

The ratios of these masses is 43.12/56.88 = 0.758:1

The mass ratio of 0.758:1 does not change no matter how the magnesium sulfide is formed or the size of the sample.

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

MgS illustrates the law of definite proportions

Laws Governing Formulas & NamesThe Law of Multiple Proportions

Water (H2O) and hydrogen peroxide (H2O2) are formed by the same two elements, they have different physical and chemical properties.

Each compound obeys the law of definite proportions in every sample of hydrogen peroxide. (16g O : 1g H)

In every sample of water, the mass ratio of O to H is always 8:1 (8g O: 1g H)

If a sample of H2O2 has the same mass of H as a sample of H2O, the ratio of the mass of O in the two compounds is exactly 2:1

Laws Governing Formulas & Names

16 g O (in H2O2 has 1g H) = 16 = 2 = 2:1 8 g O (in H2O has 1 g H) 8 1

Law of multiple proportions states that whenever the same two elements form more than one compound, the different masses of one element that combine with the same mass of the other element are in the ratio of small whole numbers.

End of Chapter 9