What determines the physical properties of a substance?
Structure and type of bonding present
Bonding determines the type of structure.
Name the types of chemical bonds.
- Ionic (or electrovalent)
- Covalent
- Dative covalent (or co-ordinate)
- Metallic
These are classified as strong bonds.
What are the weak bonds in physical bonding?
- Induced dipole-dipole interactions (London forces)
- Permanent dipole-dipole interactions
- Hydrogen bonds
Both induced and permanent dipole-dipole interactions are considered van der Waals’ forces.
Ionic bonds are formed between elements that need to _______ electrons.
lose
They gain the nearest noble gas electronic configuration.
In the formation of sodium chloride, sodium loses an electron to form _______.
Na+
Chlorine gains an electron to form Cl-.
What is the first ionisation energy (1st I.E.)?
The energy required to remove one mole of electrons from one mole of gaseous atoms
This process forms one mole of gaseous positive ions.
What are positive ions also known as?
Cations
They are smaller than the original atom.
What is electron affinity?
The energy change when one mole of gaseous atoms acquires one mole of electrons
This forms one mole of gaseous negative ions.
Negative ions are known as _______.
Anions
They are larger than the original atom due to electron repulsion.
What is the structure of ionic compounds?
Giant ionic crystal lattice
Oppositely charged ions are held together by electrostatic attraction.
What is the melting point characteristic of ionic compounds?
Very high
A large amount of energy is needed to overcome strong electrostatic attractions.
True or false: Solid ionic compounds conduct electricity.
FALSE
Ions are held strongly in the lattice and cannot move.
Covalent bonding consists of a _______ pair of electrons.
shared
One electron is supplied by each atom on either side of the bond.
What do atoms share in covalent bonding to achieve?
The nearest noble gas electronic configuration
Some atoms may not achieve an octet due to insufficient electrons.
In covalent bonding, the greater the overlap of orbitals, the _______ the bond.
stronger
This is due to the increased region in space where an electron pair can be found.
What is the molecular representation of hydrogen?
H-H
Atoms share a pair of electrons to form a single covalent bond.
In methane (CH4), how many covalent bonds does carbon form?
4
Carbon shares all 4 of its electrons to form single covalent bonds.
What is the structure of water (H2O)?
Each hydrogen atom needs one electron to complete its outer shell
Oxygen atom needs 2 electrons to complete its outer shell.
What is the requirement for each hydrogen atom to complete its outer shell?
One electron
Each hydrogen atom needs one electron to complete its outer shell.
What does the oxygen atom need to complete its outer shell?
Two electrons
Oxygen needs two electrons to complete its outer shell.
In a covalent bond, what do atoms do to share electrons?
Atoms share a pair of electrons
This sharing allows both atoms to complete their outer shells.
What is the boiling point of methane (CH4)?
-161°C
Methane has a low boiling point due to weak intermolecular forces.
What type of interactions are induced dipole-dipole interactions also known as?
London or Dispersion Forces
These occur due to the movement of electrons creating temporary dipoles.
What is the Pauling Scale used for?
Measuring electronegativity
It quantifies the ability of an atom to attract electrons in a covalent bond.
