Naming Ionic Compounds and
Covalent Molecules
•Ionic
compounds do not use prefixes in naming. This is
because the ions only bond in a ratio of their charges
• Covalent molecules require the use of prefixes in naming
molecules.
Writing chemical formulas

Use the elements symbols from the
periodic table

H2O
 H is symbol for Hydrogen
 O is symbol for Oxygen
 The # 2 is written to show the number of H, this is
call a subscript
Metals have many charges

Roman Numerals- used in ionic
compounds for metals





Gold (I) ion is Au+
Using symbols to represent numbers
Gold (II) ion is Au2+
Iron (II) ion is Fe2+
Iron (III) ion is Fe3+
Charges
Cu+ or Cl- the + and – represent the
charge
 Cu 2+ is the charge on this particular
atom of Copper.


This is called superscript
Naming Cations

Use the names of the elements.
 K+ known as potassium ion
 Zn2+ known as zinc ion

When an element forms two or more
ions, the ion names include roman
numerals to show charge
◦ Cu+ = copper (I) ion
◦ Cu2+ = copper (II) ion
Naming Anions

Name is formed from the element, but
ends in –ide
◦ Cl- is the chloride ion
◦ O2- is the oxide ion
Binary Ionic Compounds
Binary means compound is made up of
just two elements. Examples: NaCl,CaF2,
and AlCl3.
 Named as Sodium Chloride, Calcium
Fluoride and Aluminum Chloride. (Notice
they do not have prefixes in the names.)
 Cation followed by the name of the anion

◦ Positive then negative

Compounds must have no overall charge
Polyatomic Ions

Charged groups of two or more bonded
atoms that can be considered a single ion
Example is Phosphate (PO4)-3.

Charge is either positive or negative and the
number after the sign.

Many contain oxygen
◦ -ite, and –ate indicate the presence of oxygen
◦ examples: Sulfite and Sulfate
Polyatomic Ion form IONIC bonds
Polyatomic ions are negative ions, except
for ammonia, and they are found at the
end of the chemical formula.
 Example is Sodium Phosphate
 They bond in a ratio of their charges.
 Na+1 and (PO4)-3 are their charges
 Na3(PO4) is the compound’s chemical
formula.

Covalent Molecules
A bond formed when one or more PAIRS
of electrons are shared between atoms.
 Requires the use of PREFIXES, since
covalent bonds may occur in many ratios
of atoms, so we must STATE how many of
each atom are in the molecule.

Ionic or Covalent?

There are 4 good methods to tell if
something is Ionic or Covalent.
◦ Electronegativity Difference of 1.9 to 0 is a
covalent bond.
◦ If the first element is on the top ½ of the ion
sheet, then its IONIC. Likewise, if its NOT on
the top ½ of the list, it’s COVALENT.
◦ Metal plus non-metal is IONIC, and non-metal
plus non-metal is COVALENT.
◦ If an element from the right side combines
with an element from the right, it’s IONIC.
Covalent Nomenclature
If the first element is singular, then use the
whole name of the element and use
prefixes for the second element and
change the ending to “ide”
 CO = Carbon Monoxide
 CO2 = Carbon Dioxide
 NO = Nitrogen Monoxide
 NO2 = Nitrogen Dioxide

Covalent Nomenclature
If the first element in a covalent molecule
is multiple, then we must include a
PREFIX. i.e. P3O7 is named as ___?
 Triphosphorus heptaoxide
 N4O9 is named as_________?
 Tetranitrogen Nonaoxide
 H2O is commonly known as water, but
what is the proper name?
 Dihydrogen monoxide

Moles to Number of Particles
23

1 mol = 6.022 x 10 particles

6.022 x 1023 particles / 1 mol = 1
Molar Mass

The mass in grams of 1 mole of a
substance

Equal to atomic mass

1 mole = atomic mass of an element