Part 1: Covalent Bonds
And Molecules
Objectives
• Explain what a covalent bond is and
what type of elements form them
• Describe how molecules with
covalent bonds are named
2
Octet Rule
• Atoms want to achieve a noble gas
electron configuration
– s2p6
– 8 valence electrons in dot structure
• Exception is hydrogen  wants to have
two valence electrons to be like helium
(“duet rule”)
Ionic Compounds
• Ex.) NaCl
• Na achieves octet rule by losing 1 electron
and Cl achieves octet rule by gaining 1
electron
• Valence electrons get transferred from
metal to nonmetal
• Ionic compounds contain ions (cation +
anion) held together by ionic bonds
Covalent Bonds
• Some nonmetals are unlikely to lose or gain
electrons
• Ex. Nonmetal elements in Group 4 have
four electrons in their outer levels
• To gain or lose four electrons is highly
unlikely due to their protons’ attraction
Molecular Compounds
• Ex.) H2O
• No ions!!!
• All atoms are held together by
covalent bonds
• Electrons get shared so the octet
rule can be met for all atoms
• Two non-metals
Covalent Bonds
• The stable attraction
that forms between
nonmetal atoms when
they share electrons
is known as a
covalent bond
• The neutral particle
that forms due to
electron sharing is
called a molecule
• Use Lewis Dot
structures for clarity
A water molecule
Covalent Bonds
• A single covalent bond is
made up of two shared
electrons
• A water molecule contains
two single bonds in which each
atom contributes one electron
to the other in the bond
• The result: a stable outer
energy level for each atom
in the molecule:
• 2 for H and 8 for O
Molecule Example (water)
Molecule- Smallest part of molecular
compound held together by covalent bonds
Covalent Bonds
• A covalent bond also can contain more
than one pair of electrons
• An example of this is the bond in oxygen (O2)
or nitrogen (N2)
Molecule Representation
H 2O
Molecular
Formula
Structural
Formula
Naming Molecular (Covalent)
Compounds
• No molecular compounds will ever
contain metals or contain ions
• You need to forget about charges
when naming molecular compounds
Rules for Naming Molecular
Compounds
1. Use full name of first element
2. Second element uses the “root” name of the
element + the “ide” suffix.
3. Use hydrate prefixes to denote how many
atoms of each are in the compound.
Ex.) CO2 = Carbon dioxide
4. Prefix “mono” is never used in front of the 1st
element and the 2nd element only uses the
prefix “mono” if it is oxygen. Ex.) carbon
monoxide
Examples of Naming
Molecules…
•
•
•
•
OF2 •
CO •
NH3 •
P2I5 •
Oxygen difluoride
Carbon monoxide NOT monooxide
Nitrogen trihydride
Diphosphorus pentiodide (drop “a”
from penta)
• H2O • Dihydrogen monoxide
• NONE OF THESE COMPOUNDS CONTAIN METALS!!!
• HYDROGEN = NOT A METAL!!!
Objectives
• Explain what a covalent bond is and
what type of elements form them
• Describe how molecules with
covalent bonds are named
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