Module 2 - Bonding and Structure Flashcards
What are the 3 main types of
chemical bonds?
● Ionic
● Covalent
● Metallic
Define ionic bonding
The electrostatic attraction between
positive and negative ions
Give an example of a ionically
bonded substance
NaCl (Sodium Chloride - salt)
Define covalent bonding
Electrostatic attraction between a shared
pair of electrons and the nuclei
Define metallic bonding
Electrostatic attraction between the
positive metal ions and the sea of
delocalised electrons
Electrons in which shell are
represented in a dot and cross
diagram?
The outer shell
Why does giant ionic lattices
conduct electricity when liquid
but not when solid?
In solid state the ions are in fixed
positions and thus cannot move. When
they are in liquid state the ions are
mobile and thus can freely carry the
charge
Giant ionic lattices have high
or low melting and boiling
point? Explain your answer
They have high melting and boiling point
because a large amount of energy is
required to overcome the electrostatic
bonds
In what type of solvents do
ionic lattices dissolve?
Polar solvents
E.g water
Why are ionic compounds
soluble in water?
Water has a polar bond. Hydrogen atoms
have a delta + charge and oxygen atoms
have a delta - charge. These charges are
able to attract charged ions
What is it called when atoms
are bonded by a single pair of
shared electrons?
Single bond
How many covalent bonds
does carbon form?
4
How many covalent bonds
does oxygen form?
2
What is a lone pair?
Electrons in the outer shell that are not
involved in the bonding
What is formed when atoms
share two pairs of electrons?
Double bond
What is formed when atoms
share three pairs of electrons?
Triple bond
What is average bond
enthalpy?
Measure of average energy needed to
break the bond
What is a dative covalent
bond?
A bond where both of the shared
electrons are supplied by one atom
How are oxonium ions
formed?
Formed when acid is added to water,
H3O+
What does expansion of the
octet mean?
When a bonded atom has more than 8
electrons in the outer shell
What are the types of covalent
structure?
● Simple molecular lattice
● Giant covalent lattice
Describe the bonding in simple
molecular structures
Atoms within the same molecule are held
by strong covalent bonds and different
molecules are held by weak
intermolecular forces
Why do simple molecular
structures have low melting
and boiling point?
Small amount of energy is enough to
overcome the intermolecular forces
Can simple molecular
structures conduct electricity?
No, they are non conductors.
Why do simple molecular
structures not conduct
electricity?
The have no free charged particles to
move around
Simple molecular structures
dissolve in what type of
solvent?
Non polar solvents
Give examples of giant
covalent structures
● Diamond
● Graphite
● Silicon dioxide, SiO2
List some properties of giant
covalent structures? (3)
● High melting and boiling point
● Non conductors of electricity, except graphite
● Insoluble in polar and non polar solvents
How does graphite conduct
electricity?
Delocalised electrons present between
the layers are able to move freely
carrying the charge
Why do giant covalent
structures have high melting
and boiling point?
Strong covalent bonds within the
molecules need to be broken which
requires a lot of energy
Draw and describe the
structure of a diamond
3D tetrahedral structure of C atoms, with each C atom
bonded to four others
What does the shape of a
molecule depend on?
Number of electron pairs in the outer shell
Number of these electrons which are bonded and
lone pairs
What is the shape, diagram
and bond angle in a shape
with 2 bonded pairs and 0 lone
pairs?
Linear
180°
What is the shape, diagram
and bond angle in a shape
with 3 bonding pairs and 0
lone pairs?
Trigonal planar
120°
What is the shape, diagram and
bond angle in a shape with 4
bonded pairs and 0 lone pairs?
Tetrahedral
109.5°
What is the shape,diagram
and bond angle in a shape
with 6 bonded pairs and 0 lone
pairs?
Octahedral
90°
What is the shape, diagram
and bond angle in a shape
with 3 bonded pairs and 1 lone
pairs?
Pyramidal
107°
What is the shape, diagram
and bond angle in a shape
with 2 bonded pairs and 2 lone
pairs?
Non linear
104.5°
By how many degrees does
each lone pair reduce the
bond angle?
2.5°
Define electronegativity
The ability of an atom to attract the pair
of electrons (the electron density) in a
covalent bond
In which direction of the
periodic table does
electronegativity increase?
Top right, towards fluorine
What does it mean when the
bond is non-polar?
The electrons in the bond are evenly
distributed
What is the most
electronegative element?
Fluorine
How is a polar bond formed?
Bonding atoms have different
electronegativities
Why is H2O polar, whereas
CO2
is non polar?
CO2 is a symmetrical molecule, so there
is no overall dipole
What is meant by
intermolecular force?
Attractive force between neighbouring
molecules
What are the 2 types of
intermolecular forces?
● Hydrogen bonding
● dipole dipole
● dispersion
What is the strongest type of
intermolecular force?
Hydrogen bonding
What are the 2 interactions
that can be referred as Van
der Waals’ forces?
● Permanent dipole - induced dipole
interaction
● Permanent dipole - permanent dipole
interaction
Describe permanent dipole-induced dipole interactions
● When a molecule with a permanent dipole is
close to other non polar molecules it causes
the non polar molecule to become slightly
polar leading to attraction
Describe permanent dipolepermanent dipole interactions
Some molecules with polar bonds have
permanent dipoles → forces of attraction
between those dipoles and those of
neighbouring molecules
Describe London forces
● induced dipole-induced dipole attraction
● London forces are caused by random movements of
electrons
● This leads to instantaneous dipoles
● Instantaneous dipole induces a dipole in nearby
molecules
● Induced dipoles attract one another
Are London forces greater in
smaller or larger molecules?
Larger due to more electrons
Does boiling point increase or
decrease down the noble gas
group? Why?
Boiling point increases because the
number of electrons increases and
hence the strength of London forces also
increases
What conditions are needed
for hydrogen bonding to
occur?
- O-H, N-H or F-H bond, lone pair of electrons on O, F, N
- Because O, N and F are highly electronegative, H nucleus is
left exposed - Strong force of attraction between H nucleus and lone pair of
electrons on O, N, F
Draw a diagram of hydrogen
bonding
Why is ice less dense than
liquid water?
● In ice, the water molecules are arranged in a
orderly pattern. It has an open lattice with
hydrogen bonds.
● In water, the lattice is collapsed and the
molecules are closer together.
Why does water have a
melting/ boiling point higher
than expected?
Hydrogen bonds are stronger than other
intermolecular forces so extra strength is
required to overcome the forces
