Lesson 5

Molecular Elements

Many non-metal elements exist as molecules.



In these elements, the atoms are sharing valence
electrons with one another in order to fill their valence
orbitals.
The sharing of electrons is known as a covalent bond.
The atoms in these elements are still electrically neutral
as there has been no loss or gain of electrons.


Ex. Hydrogen (H2)
 Each hydrogen atom has 1 valence electron.
 The electrons can be shared between the two atoms
if they come close enough together that the orbitals
overlap.
 A single covalent bond (1 pair of electrons) is
formed.


Ex. Oxygen (O2)
 Each oxygen atom has 6 valence electrons.
 The unpaired electrons can be shared between the two atoms if
they come close enough together that the orbitals overlap.
 A double covalent bond (2 pairs of electrons) is formed.
Ex. Nitrogen (N2)
 Each nitrogen atom has 5 valence electrons.
 The unpaired electrons can be shared between the two atoms if
they come close enough together that the orbitals overlap.
 A triple covalent bond (3 pairs of electrons) is formed.
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
Ex. Fluorine (F2) and the other halogens (Cl2, Br2, I2)
 Each fluorine atom has 7 valence electrons.
 The unpaired electrons can be shared between the two atoms if
they come close enough together that the orbitals overlap.
 A single covalent bond (1 pair of electrons) is formed.
Ex. Phosphorus (P4)
 Each phosphorus atom has 5 valence electrons.
 The atoms arrange themselves into a 4-atom ring with
alternating single and double covalent bonds.
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Ex. Sulfur (S8)
 Each sulfur atom has 6 valence electrons.
 The atoms arrange themselves into an 8-atom ring
with single covalent bonds only.
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

Molecular Compounds
Each molecular compound is made up of at least 2 different types
of non-metals which share their valence electrons in covalent
bonds.
Binary molecular compounds are made up of 2 different types of
non-metal atoms. These atoms are all electrically neutral as is
the overall compound.

Unlike ionic compounds, the two non-metal elements can join
together in ratios other than the simplest whole number ratio.

For example, C2H2 (acetylene) and C6H6 (benzene) have the same
ratio but are very different compounds with different properties.


Name the first element listed. If there is only one atom of this
element in the formula do not include a prefix. If there is more
than one atom in the formula, the appropriate prefix must be
included.
Name the second element listed but give it an “ide” ending.
Always include a prefix to indicate the number of atoms of this
element in the formula.
 Prefixes
to be used:
 1. mono
6. hexa
 2. di
7. hepta
 3. tri
8. octa
 4. tetra
9. nona
 5. penta 10. deca
 CO
=
 CO2 =
 N2O =
 N2O4 =
carbon monoxide
carbon dioxide
dinitrogen monoxide
dinitrogen tetraoxide

EX. Name the following compounds:

S2O5=

P3O4
=

ClO2
=

NH3 =

EX. Write the formula for:

carbon disulfide

trinitrogen hexachloride

tetraphosphorus heptafluoride=

tricarbon octahydride=
=
=
Name of Compound
Formula of
Compound
copper(II) hydroxide
NiSO3
phosphorus tribromide
P4I8
sodium peroxide
AsF3
lead(II) chlorate
Zn(ClO4)2
strontium thiocyanate trihydrate
N2Cl4
bromine monoiodide
HgS2O3  4 H2O
silicon dioxide
MnCl4
platinum(IV) nitrite
NH4NO3
sulfur trioxide
Al(CH3COO)3
Ionic or
molecular?
Soluble or insoluble?