Covalent Compounds
Bonds… Covalent Bonds.
- Electrons jump
from one atom to
another in Ionic
Bonds
- But, in covalent
bonds, the atoms
share electrons
between one
another.
• Another reminder about electrons…
• Check combining powers of elements in
order to know how many they will share.
1
Metals lose
electrons
& become
+
2
0
3 4 3 21
Nonmetal
s gain
electrons
& become
-
Covalent Bonds—Sharing
• Some atoms are unlikely to lose or gain
electrons because the number of electrons
in their outer levels makes this difficult.
• They have a tight hold on their electrons;
they are very electronegative.
• If they won’t give up an electron, they
share them, instead!
The Covalent Bond
• The chemical bond that forms between
nonmetal atoms when they share electrons is
called a covalent bond.
The Covalent Bond
• Shared electrons are attracted to the
nuclei of both atoms.
• They move back and forth between the
outer energy levels of each atom in the
covalent bond.
• So, each atom has a stable outer energy
level some of the time.
Here’s what we mean:
The Covalent Bond
• The neutral particle is formed when atoms
share electrons is called a molecule
• A molecule is the basic unit of a molecular
compound.
Some examples of covalent bonds:
• Molecular compounds involve two nonmetals.
• They have low melting points, aren’t as
soluble in water, & are poor conductors of
heat or electricity.
More examples of covalent bonds:
The Polar Covalent Bond
• Special case of uneven sharing; water is a
polar covalent substance, due to Oxygen.
Covalent compounds: Formulae
• Both elements are nonmetals, so put the
less electronegative one first. (the one
further left on the periodic table!)
• Check the combining powers for each
element, and swap them.
• E.g.,
H = 1, O = 2  H2O
Covalent compounds: Formulae Examples
• Carbon + one oxygen = CO
• Carbon + two oxygens = CO2
• Silicon + Bromine?
• SiBr4
• Arsenic + Fluorine
• AsF3
• Nitrogen + Iodine
• NI3
• Hydrogen + Sulfur?
• H2S
Covalent compounds: Names
• Just like the formulae, write the less
electronegative one first. (the one further
left on the periodic table!)
• Change the more electronegative one’s (i.e.,
the second one’s) name to end in -ide
• Include prefixes to indicate number of
atoms, based on the combining powers.
Covalent compounds: Name Examples
• Carbon + one oxygen = Carbon monoxide
• Carbon + two oxygens = Carbon dioxide
• Silicon + Bromine?
• Arsenic + Fluorine
• Silicon
tetrabromide
• Nitrogen + Iodine
• Arsenic trifluoride
• Hydrogen + Sulfur?
• Nitrogen triiodide
• dihydrogen sulfide