EOY Exam Flashcards
Ion
An atom that has lost or gained electrons.
* Metals loose electrons and form positive ions.
* Non metals gain electrons and form negative ions.
(And atom that has become charged)
Bond
A force of attraction that holds atoms/ions together.
Electrostatic force
The strong force of attraction between positive and negative ions.
Cations
Positive ions
Anions
Negative ions
Ionic bonding
The strong electromagnetic force of attraction between cations (+) and anions (-).
Atomic number
Number of protons / electrons
Atomic mass number
Number of neutrons and protons.
Ionic lattices
Ionic compounds are made up of ions arranged in regular structures tightly packed with a repeating pattern or alternating (+) and (-) ions.
No oxygen present
‘ide’
Oxygen present
‘ate’
Ammonium (ion formula)
NH₄⁺
Carbonate (ion formula)
CO₃²⁻
Sulphate (ion formula)
SO₄²⁻
Nitrate
NO₃4⁻
Fluoride
F⁻
Chloride
Cl⁻
Bromide
Br⁻
Oxide
O²⁻
Sulphide
S²⁻
Phosphide
P3⁻
Properties of ionic compounds
(Ionic lattice)
- High melting and boiling points.
- Not conducting electricity or heat.
- Brittle
- Soluble in water
Brittle ionic lattice
The ionic lattice breaks when force is applied, because the arrangement of positive and negative ions changes and the positive and negative ions repel each other.
Soluble in water
(ionic lattice)
(Dissolves in water)
When ionic compounds are dissolved (in solution) the ions can move and conduct electricity.
Where do covalent bonds exist?
Between non-metals
e.g. C, H, O, N, S, halogens
Covalent compounds
Molecular substances.
Groups of atoms:
* That don’t form lattices
* Are held together by covalent bonds.
How are covalent bonds formed?
They are formed by atoms of non-metals sharing electrons from their outer shells.
1 covalent bond =
= 1 pair of shared electrons
What do group 7 form
The halogens form di-atomic molecules.
What is a molecule
A group of atoms bonded by covalent bonds.
Monomers
Simple molecules that can be joined in a chain.
Polymer
A chain of repeating units, all chemically bonded.
What are the forces between simple molecules?
Weak intermolecular forces of attraction.
What are the forces between the molecules of polymer chains?
Many weak inter-molecular forces of attraction along the length of the molecules.
What are the properties of simple molecules?
- low melting and boiling points
- poor conductor of electricity
- often a gas or liquid at room temperature
What are the properties of polymer chains?
- poor conductor of electricity
- solid at room temperature
Why are both simple molecules and polymers poor conductors of electricity?
There are no charge carriers (electrons) that are free to move.
Examples of simple molecules
- CO2
- H2O
- CH4
- H2
- O2
- Halogens
Example of polymer
Plastic
Where is the word allotropes from?
The Greek word for “other forms”
What are allotropes of carbon?
Different arrangements of large numbers of atoms covalently bonded to each other
What happens to carbon atoms in graphite?
- They form 3 covalent bonds
- Arranged in hexagons
- In parallel layers
How many bonds are there in diamonds?
4
Nanotubes
- Carbon atoms with 3 covalent bonds
- they form a cylinder (tube shape)
- resistant
- high melting and boiling points
- conducts electricity
Buckminster fullerenes
- carbon atoms with 3 covalent bonds
- they form a sphere (small radius)
- formula = C60
- low melting and boiling point due to weak intermolecular forces
Graphine
Consists of carbon atoms in a single layer forming large sheets
* one atom thick = light weight
* free (delocalised) electrons (conduct electricity)
Properties of metals
- Solids
- Malleable
- Good conductors of electricity
- High density
- High melting and boiling points
- Shiny and grey (except copper)
Properties of non-metals
- Mainly gases
- Brittle
- Usually don’t conduct electricity
- Low density
- Low melting and boiling points
- Dull (not shiny, colour varies)
Metallic bonding
The strong electrostatic force of attraction between the positive metal ions and the negative delocalised ions.
