CHEMICAL BONDING
Chemical Bonding
― defined as any arrangement of electron in two atoms that
generates a force, causing the atoms to be bound to each
other, forming a molecule
Periodic Groups
Group 1A: Alkali Metals
Group 2A: Alkaline-Earth
Metals
Group 3A: Boron Group
Group 4A: Carbon Group
Group 5A: Nitrogen
Group
Group 6A: Chalcogens
Group 7A: Halogens
Group 8A: Noble Gases
Valence Electrons
➢ electron in the
outermost orbital
shell
➢ electron that can
be gained or lost
➢ Noble gases,
complete valence
– most stable
Group 8 (NOBLE GASES)
➢ last electron shell
completely filled
➢ lowest tendency to
gain, lose, or share
electrons
➢ they are inert
➢ least likely to react
with other
elements
Octet Rule
➢ all atom must have
eight electrons
➢ atoms form bonds
to have 8 valence
electrons
➢ compounds
containing 8
valence electrons
are stable
➢ does not apply with
hydrogen
Lewis Structure
➢ strictly follows the
octet rule
➢ illustrations of
electrons in an
element
➢ dots surrounding
elements
represents valence
electron(s)
Chemical Bond
― an attempt to fill electron shells by
transfer (losing or gaining) or sharing of
electrons to achieve greater stability
― force of attraction that holds atoms
together
Ionic Bonding
― or elctrovalent bond
involves the transfer of
electrons from one atom
to another, usually
between a metal and a
non-metal, forming
electrically charged atoms
of ions
― the strong electrostatic
attraction between the
cation and the anion hold
them together, to form an
ionic compound
Ionic Bonding
Ionic Compounds
➢ hard and brittle
➢ form crystal lattices rather
than amorphous solids
➢ have high melting and
boiling point
➢ conduct electricity when
dissolved in water
➢ good insulators in solid state
Covalent Bonding
― formed when two
electrons are shared
between two or more
atoms resulting in the
formation of a molecule
― the shared pair of
electrons is
simultaneously being
attracted by the nuclei of
the two atoms, thus
holding them together
― generally formed between
non-metals
Covalent Bonding
Covalent Bonding
Covalency number
― number of covalent
bonds that an atom
can form within a
molecule
― number of unpaired
electrons indicates the
number of covalent
bonds
Types of Covalent Bonds
Normal Covalent bond
― formed when both atoms
donate to form the
shared pair
Coordinate covalent bonds
― formed when the
electrons that constitute
the shared electron pair
comes from only one of
the participating atoms
Bond Polarity
➢ bonding between unlike atoms results in unequal sharing of the
electrons
➢ one atom pulls the electrons in the bond closer to its side and one
end of the bond has larger electron density than the other
➢ the end with the larger electron density gets a partial negative
charge and the end that is electron deficient gets a partial positive
charge
d+
H •• Cl
d-
Bond Polarity
Polar Covalent bond
― results from unequal sharing
between two different atoms
― the greater the electronegativity
between two atoms joined by a
covalent bond, the more polar
the bond is
Nonpolar covalent bonds
― results from equal sharing of
electrons between bonded
atoms
Bond Polarity
Bond Polarity
3.0-3.0
= 0.0
4.0-2.1
= 1.9
Covalent
Pure
0
0.4
3.0-0.9
= 2.1
Ionic
Polar
2.0
Electronegativity difference
4.0
Covalent Compounds
➢ exist as gases, liquids, or
solids, made-up of
molecules
➢ tends to be soft and very
flexible
➢ low melting points and
boiling points
➢ poor electrical conductors
➢ many soluble in nonpolar
liquids
Diatomic Elements
➢ elements which cannot
exist by themselves
➢ combines with atoms of
the same element
➢ exists diatomically to be
stable
Resonance Structure
➢ molecules with two or
more Lewis structure
➢ differs only in the position
of electrons
➢ only unshared and
multiple bonded
electrons can be moved
Metallic Bond
― formed between atoms of
metallic elements
― holds metal ions very
strongly
― electron cloud around
atoms which accounts for
properties such as good
conductors at all states,
lustrous, very high melting
points
― examples; Na, Fe, Al, Au,
Co
ANY QUESTIONS???