Ion Formulas, Charges, and names

Naming Compounds and Writing Formulas

Binary Ionic Compounds

Binary ionic compounds are made up of
only two elements.

Naming - name the CATION followed by
the ANION.

❖

Name of the cation is the name of
the metal without any change.

❖

Name of the anion is the name of
the nonmetal with an -ide ending.

Metals with Multiple Ions

Groups 1 and 2 along with
aluminum (Al - group 13) form
ions with a positive charge that
is equal to their group numbers.

Groups 15, 16, 17 are a bit
different. Their charges are the
difference between the group
number and the value of 8.

Example: Group 16 would be
8-6=2 so the elements in Group
16 would have a -2 charge.

Metals with Multiple Ions

Many transition metals form more than one type of ion.

Copper has several including Cu+ and Cu2+

When naming these ions, Roman numerals are used to indicate the
charge on the ion;

Cu+ + O-2 = Copper (I) oxide Cu2O

Cu2+ + O-2 = Copper (II) oxide CuO

Polyatomic Ions

Polyatomic ions are a covalently bonded group of atoms that has a
positive or negative charge and acts as a unit.

OH hydroxide

When used in a formula and there is more than one unit, parentheses
are used around the polyatomic ion and a subscript is added that tells
how many is needed for a balanced equation:

Fe3+ + OH- = Fe(OH)3 iron (III) hydroxide

Writing Formulas for Ionic Compounds

*If you know the NAME of an ionic compound, you can write its
FORMULA!

1.

Place the symbol of the CATION first (metal) followed by the anion.

2.

Use subscripts to show the ratio of ions (how many of each kind); charges
must balance.

Na+

S2-

Na2S

2:1 Ratio

2 sodium ions for every sulfur ion

metal ion with 1+ charge

nonmetal with 2- charge

one sodium ion

two sulfur ions

Writing Formulas for Ionic Compounds

Criss-Cross Method

Use the charge to
determine the
number of each ion.

Names of Molecular Compounds

The name and formula for a molecular compound
describes the type and number of atoms in a molecule of
that compound.

The general rule in naming molecular compounds is that
the most metallic element appears first; if both
elements are in the same group, the more metallic
element will be at the bottom of the column.

●The name of the second element is changed to
end in -ide.

Example: carbon dioxide

Writing Molecular Formulas

When writing molecular formulas, write the
symbol for the elements in the order the
elements appear in the name.

Use prefixes to indicate the number of atoms of
each element in the molecule.

Writing Molecular Formulas

Example: nitrogen monoxide would be N for nitrogen
and O for oxygen. No subscripts are needed as
there are only one of each type of atom so the
formula would be NO.

N2O5 would be dinitrogen pentoxide

Multiple Choice

What is the formula for iron (III) oxide?

• FeO

• Fe (III) O

• Fe₂O₃

• Fe₃O₂

Multiple Choice

Where are the transition metals located on the periodic table?

• blue square

• red square

• yellow square

Multiple Choice

What is the name of this ion?

• fluorine 3

• iron (III)

• iron (3)

Multiple Choice

What is the name of this ion?

• copper (I)

• copper

• copper (+1)

Multiple Choice

When naming a transition metal, the numerical value of the charge is indicated by a …

• prefix

• suffix

• roman numeral following the name

• superscript after the name

Multiple Choice

Group 1 has a

• 1+ charge.

• 1- charge.

• has no charge at all.

Multiple Choice

Binary ionic compounds are made up of only

• one element.

• two elements.

• three elements.

• four elements.

Match

Match the following...

• 1

• 2

• 3

• 4

• 5

Mono

Di

Tri

Tetra

Pent

• Mono

• Di

• Tri

• Tetra

• Pent

Multiple Choice

Which of these combinations is an ionic compound made of?

• Metal and Metal

• Nonmetal and Nonmetal

• Metal and Nonmetal

• Cation and Cation

Multiple Choice

What is the charge of Cobalt (III)

• 3+

• 2+

• 8+

• 3-

Multiple Choice

Li⁺ and P^3- create...

• Li₃P

• LiP₃

• LiP

• Li₂P

Multiple Choice

What is the charge and symbol for Lead(IV)

• Pb⁴⁺

• Ld⁴⁺

• Pb^4-

• Ld^4-

Multiple Choice

What is the formula for Magnesium chloride?

• MgCl

• Mg₂Cl

• MgCl₂

• Mg₂Cl₃

Multiple Choice

How do the following two elements bond together?
Al³⁺  O^2-         

• AlO

• Al₂O₃

• Al₃O₆

• Al₃O₂

Multiple Choice

How do the following two elements bond together?
K¹⁺  S^2- 

• KS

• K₈S

• K₆S₃

• K₂S