Topic 6 Chemical Compounds Teacher Key
General outcomes:
Students will be able to describe ideas used in
interpreting the chemical nature of matter.
Students will be able to apply simplified chemical
nomenclature in describing elements, compounds and
chemical reactions.
 The students will be able to distinguish between ionic
and molecular compounds and describe the properties
of some common examples of each.
 The students will be able to read and interpret chemical
formulas for compounds of two elements and name
these compounds.
 Students will be able to assemble or draw simple
models of molecular and ionic compounds.
 Students will be able to identify and describe
chemicals commonly found in the home and write the
chemical formulas.
 112 elements can be combined together to form thousands of different
compounds
 compounds are two or more different atoms joined together in a FIXED RATIO
to form a new molecule (LAW OF DEFINITE PROPORTIONS)
 elements are held together by chemical bonds to form compounds
 chemical bonds are formed when elements gain, lose, or share electrons
 A chemical formula uses SYMBOLS and NUMERALS to represent the
composition of a pure substance.
E.g. H2O2
(hydrogen peroxide)
Each capital letter represents
an element.
The numeral indicates how many atoms of
that element are needed to create this
molecule.
 In the formula NaCl (table salt), TWO elements make up this compound.
These elements are SODIUM AND CHLORINE.
TWO atoms make up a molecule of this compound (no subscript number after
the element implies that there is only one atom of this element).
 In the formula CH4 (methane), TWO elements make up this compound.
These elements are CARBON AND HYDROGEN.
FIVE atoms make up a molecule of this compound.
1. Molecular Compounds
 a molecule is the smallest independent unit of a pure substance
 if atoms SHARE ELECTRONS, a molecular compound is formed (covalent
bond)
e.g. water is a molecular compound
methane is a molecular compound
Common characteristics molecular compounds:
1. Usually formed from only non-metallic elements.
e.g. Water – H20 Carbon Dioxide – CO2
2. They do not form ions in solutions.
3. Usually do not conduct electricity.
4. Solid, liquid, or gas at room temperature.
5. Have low boiling and melting points and the attraction between the
molecules is weak (the molecule of the compound is very strong but it
the attraction between other molecules of the compound is weak)
 Diatomic Molecules are molecules that are made of two atoms of the same
element.
e.g. oxygen gas molecule – O2
hydrogen gas molecule – H2
nitrogen gas molecule – N2
2. Ionic Compounds
 Ionic Compounds are formed from METAL and NON-METAL elements.
e.g. Salt – NaCl
e.g. Iron Oxide (Rust) – FeO2
 all atoms have equal number of Electrons and Protons which give them an
overall charge of ZERO or NEUTRAL
 When an atom GAINS or LOSES an electron, it becomes an ION. The atom
is no longer NEUTRAL because the CHARGES ARE NO LONGER
BALANCED. IONS WILL HAVE A POSITIVE OR A NEGATIVE CHARGE.
 Sodium will lose an electron in a chemical reaction so it will become a positive
ion (cation).
A Sodium atom has 11 Protons and 11 Electrons giving it a neutral charge. This means
that it has one electron in its outer shell making it very reactive. If it could lose that one
electron, it would then have a full second shell. But if it does this, then it would have 11
Protons (+11) and only 10 Electrons (-10) thus giving the overall charge of the sodium atom
+1. This then would make it a Sodium ION.
11+
Hand draw
Bohr models
for myself!
11+
Sodium Atom
Sodium Ion
 Chlorine will gain an electron in a chemical reaction so it will become a
negative ion (anion).
A Chlorine atom has 17 Protons and 17 Electrons giving it a neutral charge. Its outer shell
is missing one electron, so if it picks up one electron, then it will have a full outer shell. But
if it does this, then it would have 17 Protons (+17) and 18 Electrons (-18) giving the new
chlorine atom an overall charge of –1. It would then become a Chlorine ION.
17+
Chlorine Atom
17+
Chlorine Ion
Hand draw
Bohr models
for myself!
 These two ions will form a new compound called table salt in a ratio of 1:1
The bonds holding the compound together are called IONIC BONDS.
e- transfer
Hand draw
Bohr models
for myself!
Sodium Chloride
(a compound with properties different than either sodium or chlorine)
An Ionic Compound is formed because opposite charges attract. Just like a
magnet, the positive end attracts the negative end, so do positive ions and negative
ions that form Ionic Compounds.
NaCl
THINK: How will an ionic compound made from magnesium and
bromine combine?
Since Mg wants to lose two electrons and Br only wants to
gain one electron, two Br atoms will be required to take the
two electrons from one atom of Mg. It will combine in a 1:2
ratio. MgBr2
Common Characteristics of Ionic Compounds
1. They are very strong and have a high melting point because of
strong ionic bonds
2. They are solid at room temperature.
3. Form ions in solutions. (e.g. Salt breaks apart into it’s sodium ions and
chlorine ions in water – it’s the sodium that tastes salty! )
4. They are good electricity conductors when they are in a solution.
Naming Molecular and Ionic Compounds
 a compound made from two different elements is called a BINARY
COMPOUND
-naming of MOLECULAR BINARY COMPOUNDS and IONIC COMPOUNDS
follow the rules set out by the International Union of Pure and Applied
Chemistry (IUPAC)
To start: 1. Determine if the molecule is molecular or ionic.
*Remember: Molecular (non-metal / non-metal)
Ionic (metal / non-metal)
2. Write the entire name of the first element.
3. Change the ending on the name of the second element to -ide.
(ex. Oxygen
oxide, Fluorine
fluoride
4. If its:
Molecular
Use a prefix to indicate the number
of each type of atom in the formula:
Ionic
DO NOT include the prefixes for the
number of elements present in the
molecule
Mono for one
Di for two
Tri for three
Tetra for four
e.g. CO2
1. Molecular or Ionic?
2. Carbon
3. Oxide
4. Carbon dioxide
e.g. CCl4
1. Molecular or Ionic?
2. Carbon
3. Chloride
4. Carbon tetrachloride
e.g. NaF
1.
2.
3.
4.
e.g. Al2O3
1.
2.
3.
4.
Molecular or Ionic?
Sodium
Fluoride
Sodium fluoride
Molecular or Ionic?
Aluminium
Oxide
Aluminium oxide