Download Bonding (includes Metallic bonds)


Bonding: Explains why atoms stick
together to form molecules or formula
units

The bonding of everything is tied to the
electronic structure
*Remember electron configuration
Mg 12e- 1s2 2s2 2p6 3s2
Cl 17e- 1s2 2s2 2p6 3s2 3p5


Having a full valence (outermost s and p
orbitals) gives especially low energy, a
stable configuration – lower energy is
what the universe likes.
Covalent and ionic compounds are made
because they are lower in energy than
their individual elements; which is why
compounds form and stay together
(bonded).

Atoms can achieve a full octet (valence)
in two ways

-either by transferring an e- (ionic
bonds)

or sharing an e- (covalent bonds)

Ionic bonds occur between a metal
and a nonmetal.

They stay together because opposite
charges attract (like magnets) called
electrostatic attraction.

This happens because of very
different electronegativities.

Ionic bonds are one of the strongest
types of bonding.

Ionic bonds are very strong, so ionic
compounds are usually hard, brittle,
with very high melting points and
boiling points.

Ions are packed into repeating patterns
resulting in a crystal lattice structure.

No single particle of an ionic compound →
represented by the simplest ratio of ions,
called a formula unit.

Ionic compounds also dissolve well in water
and split up into their ions called dissociation.
Because of this, ionic compounds are known as
electrolytes b/c ions conduct a current when
dissolved in water. Good conductors of
electricity as a liquid or when dissolved in
water

Superscript = charge
H1+ O2-
Subscript = # of atoms (do not write
subscripts of 1)
H2O 2 hydrogen atoms and 1 oxygen
atom

H2O2 2 hydrogen atoms and 2 oxygen
atoms

If lithium and fluorine bond, Li+ and Fwould make LiF, because the positive 1
charge balances a negative 1 charge.
Li
F
Li1+ F1-

If lithium (Li+) and oxygen (O-2) bond, more
positive lithiums are needed to balance out
the larger negative of oxygen. It would take 2
lithiums for every 1 oxygen. To show two
lithiums are needed, a subscript of “2” is
written after the lithium, Li2O
Li
Li
O
Li1+
O2- Li1+
If an ionic compound is made from Aluminum
(Al+3) and Sulfur (S-2), the amounts of each
element needed would be:
Al+3
S-2
Al+3
S-2
S-2
Totals:
+6 and -6

So the resulting compound would be Al2S3
Al
S
Al
S
S
S-2 Al+3
S-2 Al+3 S-2
Al
S
Al
S
S
S-2 Al+3 S-2 Al+3 S-2

Calcium oxide, CaO

Potassium nitride, K3N

Magnesium phosphide, Mg3P2

Chemical bond that results from the
sharing of valence electrons to get full
octets

The great majority of covalent bonds
form between nonmetals

Groups of nonmetals combine to make units
called molecules (remember, ionic
compounds form formula units)

The bonds between the atoms in a molecule
are strong, but the attraction between the
molecules is relatively weak. These attractive
forces are known as intermolecular forces, or
van der Waals forces.

Covalent compounds usually have low
melting points and boiling points b/c
they’re easy to split apart from each
other. compounds are soft.
Examples
H20 melts at 0.0˚C

CF4 melts at –150˚ and boils at –129˚C

Many covalent compounds tend to be
gases and liquids at room temperature,
while ionic compounds are almost
always solids at 25˚C (room temp.)

Covalent compounds do not conduct
electricity

Many are polar

The only purely covalent bond is
between atoms of the same element
Hydrogen and Bromine. Hydrogen has 1
valence electron, Bromine has 7. Both need
1 more electron to form a stable noble gas
configuration…so they form a single
covalent bond
 Use Lewis dot diagrams to show electrons,
and a line to show covalent bond
H
Br
H – Br
Or
H Br

Oxygen and Hydrogen
H
O
H
H–O
H
Or
H
O
H

Carbon and Chlorine:
C
Cl
Cl
Cl
Cl – C – Cl
Cl
Cl
Cl

Carbon and Chlorine:
C
Cl
Cl
Cl
Cl
Cl
Or
Cl
C
Cl
Cl

Sulfur and oxygen

Nitrogen and hydrogen
Multiple Covalent bonds: sharing more
than 1 pair of electrons between two
atoms (double or triple bonds)
Oxygen gas, O2

O
O=O
O
Or
O O

Nitrogen gas, N2
N
N
N
N
Or
N
N

Carbon dioxide, CO2
C
O
O
O=C=O
Or
O
C
O

Polar bonds - a covalent bond in which the
electrons are not shared equally. One atom
has a greater attraction for the electrons (a
greater electronegativity), so the electrons
spend more time around that atom, creating a
slightly negative charge. The other atom then
has a slightly positive charge.

Ex. H2O: big difference in electronegativity for
oxygen and hydrogen. Oxygen pulls the
electrons most of the time creating a slightly
(-) charge, leaving the hydrogen with a slightly
(+) charge
Ionic
Formula Unit
Covalent
Smallest Unit Molecule
Transfer
Electrons
How Formed Share Electron
Strong Bonds
Repeating
Patterns
Crystal Structure
Bond Strength Weak Bonds
Shape
Geometric
Shape
VSEPR Model
Ionic
Metal To Nonmetal
Good Conductor
When Dissolved
Attraction Between
(+) Ion and (-) Ion
Cation metals
Anion nonmetal
Covalent
Forms
Between
Between
Nonmetals
Conduct Poor Conductors
Electricity
When
Forming
Unequal Sharing
= Polar Bond
Equal Sharing
= Nonpolar Bond
High Melting and
Properties Low Melting and
Boiling Points, Hard,
Boiling Points, Soft,
Brittle Solids
Solids, Liquids, or
Gases

Trying to fill outer shell (valance)

Compounds are neutral overall (no charge)

Can create many different compounds

Contains more than 1 electron/atom
http://www.youtube.com/watch?v=_M9khs87
xQ8

In metals the electrons are delocalized,
which means they do not belong to any
one atom but move freely from atom to
atom. These electrons form a sea of
electrons around the metal atoms.
Metallic bonding is the attraction
between metal atoms and the
surrounding sea of electrons.

These mobile electrons can act as
charge carriers in the conduction of
electricity or as energy conductors in
the conduction of heat, which is why
solid and liquid metals conduct heat
and electricity.

Metallic bonding accounts for many
physical properties of metals

Metals have high melting and boiling
points because of the strength of the
metallic bond

Malleability is the ability of a solid to
bend or be hammered into other
shapes without breaking since the
electrons can slide past each other
easily.
Ductility is sustaining large permanent
changes in shape without breaking b/c
the atoms can slide over each other
easily.
Ex. A piece of metal is drawn into a wire.


Heat conduction (or Thermal conduction)
is the transfer of energy between particles in
a solid. The temperature of the material
measures how fast the atoms are moving and
the heat measures the total amount of energy
due to the vibration of the atoms.
When one part of a metal is heated, the
atoms in this part vibrate faster and are
more likely to hit their neighbors. When
collisions take place, the energy is
passed on to the neighboring atoms
allowing the energy to travel through
the solid.
1. the number of electrons in the
delocalized 'sea' of electrons. (More
delocalized electrons results in a
stronger bond and a higher melting
point.)
2. packing arrangement of the metal
atoms. (The more closely packed the
atoms are the stronger the bond is and
the higher the melting point.)