Naming Ions

What is a Monatomic Ion? A monotomic ion consists of a single atom

with a positive or negative charge resulting from the loss or gain of valence electrons

A cation is an ion with a positive charge. Metals in groups 1A, 2A, and 3A form a cation with the same charge as their group number

The names of cations in these groups is the name of the element followed by ion or cation.

Example: Na+ is sodium ion or sodium cation Ca2+ is calcium ion or calcium cation

Naming Anions An anion is an atom that has gained electrons and

thus has a negative charge The charge of a nonmetal anion in group A is

determined by subtracting 8 from the group number.

Elements in group 7A have a charge of -1 (7-8=-1) The name of an anion is not the same as the

element’s name Anion names have the root of the element name

with –ide added to it. Example: A chlorine ion is called chloride, and

oxygen ion in called oxide

Practice

Fluorine IonBromine IonSelenium IonNitrogen Ion

FluorideBromideSelenideNitride

Ions of Transition Metals Transition metals do not form consitant charges

when ioninzing like elements in the A group They can form multiple ions Iron can form Fe2+ and Fe3+

These cations are named differently than others.

When naming an ion of a transition metal, write the name of the element folowed by it’s charge written in roman numerals following it.

Example: Fe2+ is written as iron (II) and Fe3+ is written as iron (III)

Exceptions Some transition metals have only one ionic

charge. The names of these elements do not have a

roman numeral These excepetions include silver (Ag+),

cadmium (Cd2+), and zinc (Zn2+)

Practice

Pb2+

Pb4+

Cr2+

Cr3+

lead (II)lead (IV)chromium (II)chromium (III)

Polyatomic Ions A polyatomic ion is an ion composed of more

than one atom. The names of most polyatomic ions in in –ite

or –ate. All polyatomics ending in –ite or –ate contain

oxygen

Charge Name Formula

1+ ammonium NH4+

1- acetate C2H3O2-

1- chlorate ClO3-

1- hydroxide OH-

1- cyanide CN-

1- nitrate NO3-

1- nitrite NO2-

1- perchlorate ClO4-

1- permanganate

MnO4-

2- carbonate CO32-

2- sulfate SO42-

2- sulfite SO32-

3- phosphite PO33-

3- phosphate PO43-

Adding Hydrogen When the formula for a polyatomic ion contains

hydrogen, it is a combination of an H+ ion and another polyatomic ion

H+ + CO32- (carbonate) -> HCO3

- hydrogen carbonate

H+ + PO43- (phosphate) -> HPO4

2- hydrogen phosphate

Naming Compounds with Polyatomic Ions Naming a compound with a polyatomic ion

works the same as with other ionic compounds

Name the cation first then the anion Use the name of the polyatomic ion when

naming.

Example

Naming and Writing Ionic Compounds

What is a Binary Ionic Compound A binary ionic compound is composed of two

elements joined by an ionic bond. To name a binary ionic compound place the

name of the cation first, followed by the name of the anion.

The compound must remain neutral Example: NaBr would be sodium bromide Example: CuO would be copper (II) oxide This is known because the charge of oxygen is

a 2-, so copper must have a charge of 2+ for the compound to be neutral

Cu2OSnF2

SnS2

copper (I) oxide

tin (II) fluoridetin (IV) fluoride

Writing formulas for binary ionic compounds If you know the name of a binary ionic

compound, you can write it’s formula The net charge of the compound must be zero First figure out the charge of the atoms in the

name of the compound Then use the charge of one compound as the

subscript for the other compound Then reduce to the lowest whole number ratio

Example Write the formula for calcium sulfide From the periodic table, the charge of calcium

is 2+ From the periodic table, the charge of sulfur is 6 -8 = -2 or S2-

Ca2+ and S2- crossing the charges gives Ca2S2

Reducing to the lowest whole number ratio gives CaS

Example Write the formula for iron (III) oxide From the name of the ionic compound, the

charge of iron is Fe3+

From the periodic table, the charge of oxygen is

6 -8 = -2 or O2-

Fe3+ and O2- crossing the charges gives Fe2O3

Practice

copper (II) sulfide

potassium nitride

CuS

K3N

Compounds with Polyatomic Ions Compounds with polyatomic ions behave the

same as those without The method for writing their formula is the

same as ordinary ionic compounds, except you look up the charge from a table of polyatomic ions instead of the periodic table

Example Write the formula for calcium nitrate From the periodic table, the charge of calcium

is 2+ From the polyatomic table, the charge of

nitrate is 1- Ca2+ and NO3

- crossing the charges gives Ca(NO3)2

For a polyatomic ion, the subscript is written on the outside of the parenthesis