P1: 3 Bonding Flashcards
What does ionic bonding involve?
Strong electrostatic attraction between oppositely charged ions in a lattice.
What does a single covalent bond contain?
A shared pair of electrons.
What do multiple covalent bonds contain?
Multiple shared pairs of electrons.
What does a co-ordinate (dative covalent) bond contain?
A shared pair of electrons with both electrons supplied by one atom.
What does metallic bonding involve?
Attraction between delocalised electrons and positive ions arranged in a lattice.
What are the four types of crystal structure?
Ionic.
Metallic.
Macromolecular (giant covalent).
Molecular.
What are bonding and lone pairs of electrons?
Charge clouds that repel each other.
What do pairs of electrons in the outer shell do?
Arrange themselves as far apart as possible to minimise repulsion.
What type of repulsion is greater in pairs of electrons?
Lone pair - lone pair. (greatest)
Lone pair - bond pair.
Bond pair - bond pair (weakest)
What is electronegativity?
The power of an atom to attract the pair of electrons in a covalent bond.
What produces a polar covalent bond?
The electron distribution in a covalent bond between elements with different electronegativities will be asymmetrical.
What shape and bond angle does 2 bonding pairs and 0 lone pairs make?
Linear, 180
What shape and bond angle does 3 bonding pairs and 0 lone pairs make?
Trigonal planar, 120
What shape and bond angle does 2 bonding pairs and 1 lone pair make?
Bent (V-shape), 118
What shape and bond angle does 4 bonding pairs and 0 lone pairs make?
Tetrahedral, 109.5
What shape and bond angle does 3 bonding pairs and 1 lone pair make?
Trigonal pyramidal, 107
What shape and bond angle does 2 bonding pairs and 2 lone pairs make?
Bent V-shape, 104.5
What shape and bond angle does 5 bonding pairs and 0 lone pairs make?
Trigonal bipyramidal, 120 and 90
What shape and bond angle does 4 bonding pairs and 1 lone pair make?
Trigonal pyramidal, 119 and 89
Or
See-saw, 119, 89
What shapes and bond angles does 3 bonding pairs and 2 lone pairs make?
Trigonal planar, 120
Or
T-shape, 89
What shape and bond angle does 6 bonding pairs and 0 lone pairs make?
Octahedral, 90
What shape and bond angle does 5 bonding pairs and 1 lone pair make?
Square pyramid, 89
What shape and bond angle does 4 bonding pairs and 2 lone pairs make?
Square planar, 90
What are the rules for working out the shape of molecules and ions?
- How many electrons are around the central atom?
- Add 1 electron for each bond.
- Add 1 electron for a negative charge, deduct 1 electron for a positive charge.
- Divide total by 2 to give number of pairs.
- How many bonding pairs and lone pairs?
- Arrange electrons in space to minimise repulsion.
- Treat double bonds as a single unit.
What is the formula of the compound ion sulfate?
SO4 2-
What is the formula of the compound ion hydroxide?
OH -
What is the formula for the compound ion nitrate?
NO3 -
What is the formula for the compound ion carbonate?
CO3 2-
What is the formula for the compound ion ammonium?
NH4 +
What are the melting and boiling points of molecular substances influenced by?
The strength of the intermolecular forces.
What are the intermolecular forces in order of strength?
Van der Waals
Permanent dipole-dipole forces
Hydrogen bonding
Where are van der Waal’s forces present?
In all molecular substances.
Why do van der Waal’s forces occur?
Electrons are constantly moving around so there will always be an uneven electron distribution (partly due to electronegativity).
This causes a temporary dipole within a molecule.
This induces a temporary dipole in a neighbouring molecule.
There is an attraction between these molecules - temporary induced dipole-dipole attraction.
What affects the power of van der Waal’s forces?
The bigger the molecule, the greater the van der Waal’s forces.
Where does permanent dipole-dipole attraction occur?
Between polar molecules.
Where does hydrogen bonding occur?
Where an H atom is bonded to a very electronegative atom.
Only fluorine, oxygen and nitrogen.
How does a hydrogen bond occur?
The polar bond between the H and F/O/N atom leaves the H nucleus exposed.
Therefore, there is a strong attraction from the lone pair on the F/O/N of one molecule to the exposed H nucleus of another molecule.
This is the strongest intermolecular force.
What are the properties of substances with ionic bonding?
High melting/ boiling points.
Typically solid at rtp.
Doesn’t conduct electricity except when liquid.
Soluble in water.
What are the properties of substances with molecular bonding?
(Simple covalent)
Low melting and boiling points.
Typically solid at rtp (except for I2 which is solid).
Doesn’t conduct electricity.
Solubility depends on how polarised the molecule is.
What are the properties of substances with macromolecular bonding?
High melting and boiling points.
Typically solid at rtp.
Doesn’t conduct electricity (except graphite)
Sublimes rather than melts.
Not soluble in water.
What are the properties of substances with metallic bonding?
High melting/ boiling points.
Typically solid at rtp.
Does conduct electricity.
Not soluble in water.
What is the structure of diamond?
A macromolecular allotrope of carbon.
There is covalent bonding between every carbon atom.
What is the structure of graphite?
A macromolecular allotrope of carbon.
Has strong covalent bonds between carbon atoms but weak van der Waals forces between layers.
What is the structure of iodine?
A molecular crystal.
There is a strong covalent bond that holds two iodine molecules together.
Since iodine molecules have a large number of electrons, the van der Waals forces are strong enough to hold the molecules together as a solid.
But van der Waals are much weaker than covalent bonds.
Why do some molecules with polar bonds not have a permanent dipole?
Overall, the molecule isn’t polar.
What is the structure of sodium chloride?
Giant ionic lattice.
What is the structure of magnesium?
Giant metallic lattice.
What is the structure of ice?
Lattice.
Less dense than water.
