Edexcel Additional Chemistry (C2) Revision – Mrs. Moon

Mendeleev Explain how Mendeleev arranged the

elements in a periodic table Predict the properties of missing

elements Classify elements as metals or non-

metals

The structure of an atom

The structure of an atom (again!)Learn this!

particle position charge mass symbol

proton nucleus +1 1 p

Neutron nucleus 0 1 n

electron Shell/orbital -1 ~0 e

The Periodic table – you don’t need to remember them, just know what the numbers mean

What do the numbers mean?

Atomic Number (number of protons)

Element symbol

Atomic mass

The Atomic mass is always the biggest numberAtomic mass = number of protons + number of neutrons

Columns down = groupsAnd indicate how many electrons are in the outer shell

Rows across are called = periods and indicate how manyElectron shells the element has

Isotopes - H

H paper - Isotopes An isotope has

the same number of protons, but a different number of neutrons – so –

The atomic number will be the same, but the mass number is different

Electron (always negative) Atoms have the same number of

electrons as they do protons/Atomic number

Helium – Atomic number 2, proton number 2, electron number 2

Neon – atomic number 10, proton number 10, electron number 10

Simples!

Electron shells Electrons are like soldiers on parade– they are

arranged in a very specific order! 2, 8, 8

Period table and electron shells

Ions are atoms that have lost or gained electrons Atoms like full outer shells and

chemical reactions are atoms achieving this

One way is by becoming an ion

Ionic bonds

Ionic Bonds

when electrons have been given away or received, those atoms become either positive or negative

Positives and negatives attract

Forming an ionic bond

Ionic compounds

Ionic compounds can keep growing andgrowing and become very big – like salt

Ionic compounds are formed between metals and non-metals

Ionic bondsCations Anions

What are cations?Cations are atoms which loses electrons to obtain a noble gas structure. Hence, it has a positive charge. e.g A magnesium atom (An atom of a metal) loses two electrons to form a magnesium ion in its compound.

What are anions?Anions are atoms which gains electrons to obtain a noble gas structure. Hence, it has a negative charge. e.g A chlorine atom (An atom of a non-metal) gains an electron to form a chloride ion in its compound.

Ionic compounds Working out a formula

Formula of ionic compoundsCa looses 2 electronsSo becomes +2

Cl gains 1 electron so becomes -1

(remember electronsare -1=negative

To make a zero chargeyou will need 2 x Cl-1 to cancel out Ca+2

Try the last 3 yourself

Properties of ionic compounds

H paper To conduct electricity an ionic compound must:

Contain charged particles (be positive or negative)

Be free to move (in solution)

Ion tests

Some key words to know Soluble – will dissolve into a liquid Insoluble – will not dissolve in a liquid A salt – and acid + an alkali Precipitates – an insoluble solid appears

at the end of a reaction State symbols; (s) = solid; (l) = liquid; (g) = gas; (aq) = aqueous/in water

Covalent bonds – share electronsto gain a full outer shell

Properties of covalent substances

Covalent bonds

Properties of covalent structures

H paper Most covalent compounds are tiny

molecules and gases e.g. carbon dioxide Diamond and graphite are unusual as

they are covalent, but giant compounds A why is graphite used as a lubricant

(reduces friction – makes things slippy)

Properties of covalent substances

Miscible or immiscible

Metallic bonding

Alkali Metals

Halogens

Nobel Gases

StructureNoble gases are in group 0. This means they have a full outer electron field, this makes them un-reactive. This also means they are monatomic - do not join with other elements that are the same, but are single and alone.As you move down the periods, the gases have an increasing boiling point and also density.UsesProbably the most famous noble gas is Helium, as it is used in balloons. This is because it 'floats' due to the fact it is less dense than air, so rises above it, and is completely safe since it is un-reactive. However, the densities increase as you go down the group.

Rates of reaction

Collision theory