Ionic
Between metals and nonmetals
Covalent
Between nonmetals
Metallic
Between metals
When do metals form cations?
When lose electrons to become positive ions
When do nonmetals become anions?
Gain electrons to become negative ions
What is ionic bonding?
Strong electrostatic forces of attraction between oppositely charged ions in a lattice
When's electrostatic attraction stronger?
The ions are smaller
The charges are higher
What are the properties of ionic lattices?
High melting point
Conduct electricity when molten
Why do ionic compounds have high melting points?
Strong electrostatic forces of attraction between oppositely charged ions which require a large amount of energy to break
Why don't ionic compounds conduct electricity as a solid?
The ions are in a fixed lattice so can't move to carry the charge
Why can ionic compounds conduct electricity when aqueous or molten?
The ions are free to move and carry the charge
Ions larger down the group will be…
Larger as they have more electron shells
If ions have the same number of electrons, the comparative size …
Depends on the number of protons (nuclear charge)
How does the number of protons affect the size of the ion and why?
The higher the number of protons the smaller the ion is there will be a stronger attraction between the nucleus and the outer electrons
When does the strength of electrostatic forces increase?
As size decreases
As charge increases
What does monatomic mean?
Individual atoms not bonded
What is metallic bonding?
Electrostatic force of attraction between the positive metal ions and the delocalised electrons
Where do the delocalized electrons come from in metallic bonding?
The electrons in the outer shell of the metal atoms
The strength of the metallic bond depends on…
Size of the ion (smaller = stronger)
Number delocalized electrons per iron (more=stronger)
What are the properties of metallic bonding?
Conducts electricity
Malleable
Ductile
What does ductile mean?
It can be drawn into wires
Why does metallic bonding have high melting points?
The strong attraction between the positive ions and delocalised electrons require a large amount of energy to break
Why can metallic compounds conduct electricity?
There are delocalized electrons which can move through the structure and carry the charge
Why can metallic compounds be shaped (why are they malleable)?
They are all ions of the same size in regular layers second slide over each other and be shaped
Still maintain strength is delocalized electrons can reform metallic bonds in new shape
What are the four types of crystal structures?
Bionic
Simple molecular
Giant covalent/macromolecular
What's a single covalent bond?
A shared pair of electrons with one electron coming from each of the atom in the bond
What are simple molecular compounds made from?
Small molecules
What bonds/forces are found in simple molecular compounds?
Van Der Waals
What forces are broken in simple molecular compounds when melted?
What bonds aren't broken when simple molecular compounds are melted or boiled?
What are the intermolecular forces between molecules in simple molecular compounds?
What are the properties of simple molecular compounds?
Low MP and BP
Can’t conduct electricity
Why do simple molecular compounds have a low MP and BP?
Weak van Der Waals forces between molecules which don't require a lot of energy to break (covalent bonds don't need to be broken)
Why can't simple molecular compounds conduct electricity?
No free/delocalised electrons which can move and carry a charge
What can group 4 elements form?
Giant covalent/macromolecular structures
What are macromolecular structures?
Giant molecules with covalent bonding
Give 3 examples of giant covalent structures
Diamond
Graphite
SiO2
What are the properties of giant covalent structures?
High MP
Graphite conducts electricity (SiO2 and diamond don't)
Soft
Which giant covalent structures conduct electricity?
Why do giant covalent structures have a high MP?
Covalent bonds need to be broken for substance to melt and this requires large amounts of energy
Why does graphite conduct electricity?
Contains delocalised between the layers which can move and carry a charge
Why can't diamond and SiO2 conduct electricity?
No delocalised electrons which can move through structure and carry a charge
Why are giant covalent structures soft?
Only contain weak van Der Waals forces between layers so can slide over each other
What are the 4 types of crystal structures?
Giant covalent
What type of process is melting/boiling and why?
Endothermic as requires energy to overcome intermolecular forces
What are the 3 types of intermolecular forces?
Permanent dipole-dipole
Hydrogen bonding
What's the strongest type of intermolecular force?
What's the weakest type of intermolecular force?
What are van Der Waals forces also called?
Induced dipole-dipole
Where do van Der Waals forces occur?
Between simple molecular compounds and atoms of noble gases
Which molecules have larger bps and why?
Larger molecules as have more electrons so stronger van Der waals which requires more energy to overcome
How are van Der waals forces formed?
Uneven distribution of electrons in one molecule induces a dipole in nearby molecule and the S- is attracted to S+ of neighbouring molecule
Permanent dipole-dipole forces are common in molecules with …
C-Cl
C-F
C-Br
H-Cl
C=O
What forces are found in polar molecules?
Weak electrostatic forces of attraction between S+ and S- charges on neighbouring molecules
Why do polar molecules have higher bps?
Have stronger van Der waals forces
If a molecule has hydrogen bonding, what won't it have?
Dipole-dipole forces
If a molecule has dipole-dipole forces, what won't it have?
When does hydrogen bonding occur?
When hydrogen is covalently bonded to F, N or O and the F/N/O has a lone pair of electrons
What is a hydrogen bond formed between?
Lone pair of F/N/O and S+ on another molecule
A hydrogen bond is a
Why is ice less dense than water?
When solid, water molecules in ice arrange themselves to have most hydrogen bonds possible
Each water molecule has 2 hydrogen bonds from lone pairs to neighbouring water molecules, so each molecule has 4 hydrogen bonds - means water molecules held further apart in ice than liquid water
What's electronegativity?
The power of an atom to attract a pair of electrons in a covalent bond
What's electronegativity measured between?
0-4
What's electronegativity measured on?
Pauling scale
What does a higher electronegativity number mean?
Atom can attract electron pair better
What's the most electronegative element?
Fluorine (4.0)
When does electronegativity increase?
Across a period
Down a group
Why does electronegativity increase across a period?
Number of protons/nuclear charge increases
Elements have same shielding
Why does electronegativity increase down a group?
Shielding increases as down a group
Outer electrons get further away from nucleus
What determines the type of bond between 2 atoms?
The difference in electronegativity
Large electronegative difference
>2.0
Ionic bond
Same or similar electronegative difference
<0.5
Non polar covalent bond
Electronegative difference of 0.5-1.7
Polar covalent bond
When does a polar covalent bond form?
When there's unequal distribution of electrons in bond and produces a difference in charge (dipole)
S+
Less electronegative atom
S-
More electronegative atom
Symmetrical molecules
No lone pairs
All bonds identical
Non-symmetrical molecules
Lone pairs
Non-identical pairs
When will a molecule have a permanent dipole?
When the charges are distributed unevenly
What's a dative/coordinate bond?
Contains shared pair of electrons with both electrons supplied by one atom
What's a coordinate bond shown by?
Arrow from atom that's donated
How do you explain shape and bond angles?
State no bonding and lone pairs
Electron pairs repel so bonds move as far apart as possible to minimise repulsion
If no lone - bonding pairs repel equally
If lone - lone pairs repel more than bonding so bond angle reduced by 2.5° per lone
State name and shape
2 e pairs
No lone
Linear
3 e pairs
Trigonal planar
1 lone
V shape
4 e pairs
Tetrahedral
Trigonal pyramidal
2 lone
5 e pairs
Trigonal bipyramidal
See saw
T shape
3 lone
6 e pairs
Octahedral
Square pyramid
Square planar
V shape (3e)
V shape (4e)
Linear (5e)
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