Everything for Chemistry C2

Chemistry

Atoms, Compounds and Isotopes

The mass number = Number of protons + number of neutrons

The atomic number = the number of protons

Number of protons = the number of electrons

Number of neutrons = the mass number - proton number

Atoms of the same element have the same number of protons.

Particle

Relative charge

Relative mass

Protons

+1

1

Electrons

-1

Very small

Neutrons

Neutral

1

Compounds - Compounds are formed when atoms of two or more elements are chemically combined together. It is difficult to separate the two original elements out again. E.g. Carbon Dioxide

Isotopes - Different atomic forms of the same element, which have the same number of protons but a different number of neutrons. E.g. Caron-12 and Carbon-14

Ionic bonding

Ions - Particles formed from atoms which have lost or gained electrons.

Positive ions have lost electrons

Negative ions have gained electrons

The elements that readily form ions are in groups 1,2,6 and 7

The overall charge of an ionic compound is 0

All atoms on the left hand side of the periodic table have just one or two electrons in their outer shell, so they want to get rid of them to make the element stable - this leaves the element as an ion.

On the other side, the elements in Groups 6 and 7, have outer shells which are nearly full, so they want to gain an electron to gain a full outer shell and become an ion.

Ionic bonding is formed between metals (forming positive ions) and non-metals (forming negative ions) by losing or gaining electrons

Metals lose electrons to get a full outer shell and non-metals gain electrons to get a full outer shell

Ionic bonding between atoms is done in order for both ions to have a full outer shell

The overall charge of an ion is always 0

Ionic compounds always have a regular lattice arrangement

There are very strong electrostatic forces of attraction between the oppositely charged ions in all directions, this makes them very strong

Properties of Ionic substances

1. High melting and boiling points due to strong attraction between bonds

2. Soluble in water. The ions separate and are free to move in the solution

3. Do not conduct electricity in a solid state because the ions are in fixed positions

4. Do conduct electricity when molten or in solution because ions can move around

5. Brittle

Covalent Bonding

Covalent Bonding - It is formed by sharing electrons, where each atom contributes  1 electron into a shared pair

Atoms only share electrons from their outer shell

There are two electrons in a single covalent bond

It is done so that both atoms have a full outer shell

Substances with covalent bonds can either be simple molecules or giant structures

Properties of molecular covalent substances

1. Do not conduct electricity in any state because they do not have any free electrons or ions

2. Low melting and boiling points because the forces of attraction between the molecules are weak

3. Insoluble in water

4. Most…