Chemical bonding
Intramolecular Bonds
Define an intramolecular bond as a bond which occurs between atoms within
molecules
Define A covalent bond as a sharing of at least one pair of electrons by two
non-metal atoms
Define a Non-polar covalent (pure covalent) as an equal sharing of electrons
Define a Polar covalent as unequal sharing of electrons leading to a dipole
forming (as a result of electronegativity difference)
Define electronegativity as a measure of the tendency of an atom to attract a
bonding pair of electrons
Use electronegativity numbers to determine the specific type of covalent bond
and know that
- a zero difference in electronegativity indicates a non-polar (pure) covalent
bond
- a non-zero difference in electronegativity indicates a polar covalent bond
- the greater the difference in electronegativity the more polar the bond
Define an ionic bond as a transfer of electrons and subsequent electrostatic
attraction
Know that ionic bonding is generally between metals (or ammonium ions) and
non-metals (or polyatomic ions)
Define metallic bonding as being between a positive kernel and a sea of
delocalised electrons
Intermolecular Forces
Identify that in a liquid or a solid there must be forces between the molecules
causing them to be attracted to one another, otherwise, the molecules would
move apart and become a gas.
Chemical bonding 1
, Define intermolecular force as a weak force of attraction between molecules,
ions, or atoms of noble gases
Distinguish between intermolecular forces and intramolecular bonds
State that van der Waals forces are intermolecular forces
Name and explain the origin of the following different types of van der Waals
forces:
- Dipole-dipole forces/interactions
- London forces (induced dipole or dispersion forces)
- Hydrogen bonding as a special case of dipole-dipole forces
Know that hydrogen bonds exist between polar molecules in
which hydrogen is bonded to:
- a small atom
- of high electronegativity
- with at least one lone pair of electrons
Know that all interactions between particles involve some sort of London
forces.
Explain how the strength of London forces is influenced by the size of the
temporary dipoles, which is influenced by:
- The number of electrons
- The interacting surface of the molecule (e.g. long unbranched
chain vs branched chain – see organic chemistry section)
Identify the predominant (strongest) intermolecular force in a substance
Intramolecular Bonding
Intramolecular bonds or forces are the forces or bonds that hold atoms
together within a molecule
Intermolecular forces or bonds are forces or bonds that exist between
molecules
💡 To remember which is which: the "a" in the word "intra" stands for atoms
Chemical bonding 2
, 💡 Intermolecular and intramolecular forces won't always be shown in
diagrams so we must be able to identify where these types of forces are
present
Now you try identifying where intramolecular forces and intermolecular forces
are in compounds
Identify the intramolecular forces and intermolecular forces in this compound:
Chemical bonding 3
, Answer
Intramolecular forces present between the 2 I atoms in the molecules and
intermolecular forces present between these 2 molecules
Here's a harder example:
Answer
Red dotted lines are intermolecular forces and black straight lines represent
intramolecular forces. C2H6 is one molecule.
So now that we know the difference between intramolecular and intermolecular
forces, we can look into chemical bonding
💡 When we talk of chemical bonding we are dealing with the intramolecular
bonds that form between atoms to produce molecules
When atoms bond with one another, their valence or free electrons (obtained
from their group number on periodic table) are involved in this process
The number of bonds an atom can form is referred to as its valency and is also
obtained from the atoms' group number. For groups 1-4, the valency is the same
as the group number but for groups 5-8, the valency is equal to 8 minus the
group number
Chemical bonding 4
, We have different types of chemical bonds namely covalent, ionic and metallic
bonds
Covalent bonds occur between 2 non-metal atoms. They involve sharing of
electrons. To form a bond, the two atoms must approach each other in such a
way that their half-filled orbitals overlap (remember from aufbau that non-
metals will always have an unfilled orbital(s)). The shared pair of electrons is
called the bonding pair. The other pairs of electrons that are not shared are
called lone pairs. Covalent bonds can be single (one electron pair shared),
double (2 electron pairs shared) and triple bonds (3 electron pairs shared).
Covalent bonds can either be pure (non-polar) or polar.
💡 a zero difference in electronegativity indicates a non-polar (pure)
covalent bond and a non-zero difference in electronegativity indicates a
polar covalent bond. The greater the END is, the more polar the bond is
Chemical bonding 5
Intramolecular Bonds
Define an intramolecular bond as a bond which occurs between atoms within
molecules
Define A covalent bond as a sharing of at least one pair of electrons by two
non-metal atoms
Define a Non-polar covalent (pure covalent) as an equal sharing of electrons
Define a Polar covalent as unequal sharing of electrons leading to a dipole
forming (as a result of electronegativity difference)
Define electronegativity as a measure of the tendency of an atom to attract a
bonding pair of electrons
Use electronegativity numbers to determine the specific type of covalent bond
and know that
- a zero difference in electronegativity indicates a non-polar (pure) covalent
bond
- a non-zero difference in electronegativity indicates a polar covalent bond
- the greater the difference in electronegativity the more polar the bond
Define an ionic bond as a transfer of electrons and subsequent electrostatic
attraction
Know that ionic bonding is generally between metals (or ammonium ions) and
non-metals (or polyatomic ions)
Define metallic bonding as being between a positive kernel and a sea of
delocalised electrons
Intermolecular Forces
Identify that in a liquid or a solid there must be forces between the molecules
causing them to be attracted to one another, otherwise, the molecules would
move apart and become a gas.
Chemical bonding 1
, Define intermolecular force as a weak force of attraction between molecules,
ions, or atoms of noble gases
Distinguish between intermolecular forces and intramolecular bonds
State that van der Waals forces are intermolecular forces
Name and explain the origin of the following different types of van der Waals
forces:
- Dipole-dipole forces/interactions
- London forces (induced dipole or dispersion forces)
- Hydrogen bonding as a special case of dipole-dipole forces
Know that hydrogen bonds exist between polar molecules in
which hydrogen is bonded to:
- a small atom
- of high electronegativity
- with at least one lone pair of electrons
Know that all interactions between particles involve some sort of London
forces.
Explain how the strength of London forces is influenced by the size of the
temporary dipoles, which is influenced by:
- The number of electrons
- The interacting surface of the molecule (e.g. long unbranched
chain vs branched chain – see organic chemistry section)
Identify the predominant (strongest) intermolecular force in a substance
Intramolecular Bonding
Intramolecular bonds or forces are the forces or bonds that hold atoms
together within a molecule
Intermolecular forces or bonds are forces or bonds that exist between
molecules
💡 To remember which is which: the "a" in the word "intra" stands for atoms
Chemical bonding 2
, 💡 Intermolecular and intramolecular forces won't always be shown in
diagrams so we must be able to identify where these types of forces are
present
Now you try identifying where intramolecular forces and intermolecular forces
are in compounds
Identify the intramolecular forces and intermolecular forces in this compound:
Chemical bonding 3
, Answer
Intramolecular forces present between the 2 I atoms in the molecules and
intermolecular forces present between these 2 molecules
Here's a harder example:
Answer
Red dotted lines are intermolecular forces and black straight lines represent
intramolecular forces. C2H6 is one molecule.
So now that we know the difference between intramolecular and intermolecular
forces, we can look into chemical bonding
💡 When we talk of chemical bonding we are dealing with the intramolecular
bonds that form between atoms to produce molecules
When atoms bond with one another, their valence or free electrons (obtained
from their group number on periodic table) are involved in this process
The number of bonds an atom can form is referred to as its valency and is also
obtained from the atoms' group number. For groups 1-4, the valency is the same
as the group number but for groups 5-8, the valency is equal to 8 minus the
group number
Chemical bonding 4
, We have different types of chemical bonds namely covalent, ionic and metallic
bonds
Covalent bonds occur between 2 non-metal atoms. They involve sharing of
electrons. To form a bond, the two atoms must approach each other in such a
way that their half-filled orbitals overlap (remember from aufbau that non-
metals will always have an unfilled orbital(s)). The shared pair of electrons is
called the bonding pair. The other pairs of electrons that are not shared are
called lone pairs. Covalent bonds can be single (one electron pair shared),
double (2 electron pairs shared) and triple bonds (3 electron pairs shared).
Covalent bonds can either be pure (non-polar) or polar.
💡 a zero difference in electronegativity indicates a non-polar (pure)
covalent bond and a non-zero difference in electronegativity indicates a
polar covalent bond. The greater the END is, the more polar the bond is
Chemical bonding 5
