1
Bonding – Learning Outcomes
 State what a molecule is.
 Recall that ionic bonding is an attraction between
positive and negative ions.
 HL: Describe ionic bonding using NaCl and MgO as
examples.
 Understand that covalent bonds involve the sharing of
pairs of electrons.
 HL: Describe the bonding in H2, O2, H2O, CH4 as
examples of covalent bonding.
 HL: Investigate the ability of ionic and covalent
substances to conduct electricity.
2
Define Ionic Bonding
 All atoms “want” to have a full outer electron shell.
 First shell is full with 2 electrons.
 Second and third shells are full with 8 electrons.
 Atomic bonding is when atoms lose, gain, or share
electrons to gain a full outer electron shell.
 The combination of two or more atoms bonded
together is called a molecule.
 It is the smallest particle of an element or compound
that can exist on its own.
3
Define Ionic Bonding
 Atoms on their own are usually neutral – they have the
same number of positive protons and negative
electrons.
 If an atom loses electrons, it has more positive protons
than negative electrons, becoming a positive ion.
 If an atom gains electrons, it has more negative
electrons than positive protons, becoming a negative
ion.
4
Define Ionic Bonding
 An ionic bond is formed from the force of attraction
between two oppositely charged ions.
 Consider sodium [2, 8, 1] and chlorine [2, 8, 7]
5
Describe Ionic Bonding
 Sodium can give up one electron to gain a full outer
shell.
 Chlorine will get a full outer shell if it gains one electron.
6
Describe Ionic Bonding
 If sodium gives its outer electron to chlorine, they will
both have full shells.
7
Describe Ionic Bonding
 This will make sodium positively charged and chlorine
negatively charged.
8
Describe Ionic Bonding
 The positive and negative ions are attracted to each
other and form an ionic bond, creating sodium chloride,
NaCl.
9
Describe Ionic Bonding
 Describe the ionic bond between magnesium and
oxygen:
1. Write out the electron configuration for each atom.
2. Think about how to give each atom a full outer shell.
3. Draw out the final ions that are bonded together.
10
Understand Covalent Bonds
 In ionic bonds, atoms gain or lose electrons.
 Atoms want to have full outer shells, but they also don’t
like to give up electrons.
 In some cases, electrons are shared between atoms.
11
Describe the Bonding in H2
 A pair of hydrogens can’t agree on which should give
up an electron, so they share theirs.
12
Describe the Bonding in CH4
 Carbons [2, 4] have 4 electrons in their outer shell, so can
form up to four bonds.
 Hydrogen [1] can only form one bond as it only has one
outer electron.
13
Describe the Bonding in CH4
 Thus, one carbon
bonds with four
hydrogens.
14
Describe Covalent Bonding
 Draw the covalent bond formed in oxygen gas (O2) and
water (H2O).
1. Write out the electron configuration for each atom.
2. Think about how to give each atom a full outer shell.
3. Draw out the final molecules that are bonded together.
15
Investigate Conduction in Ionic and
Covalent Substances
1. Prepare a sample of salt water
and a sample of tap water in
separate beakers.
2. Connect a light bulb in series with
a power supply and the beaker
of salt water.
3. Note that the bulb lights with
sufficient voltage.
4. Replace the beaker of salt water
with the beaker of tap water.
5. Note that the bulb does not light.
16
Investigate Conduction in Ionic and
Covalent Substances
6. The bulb only lights when in the
salt water solution.
7. As salt water is ionic and tap
water is covalent, this suggests
that ionic substances conduct
electricity, while covalent
substances do not.