# Edexel Chemisrty Paper 1 - Revision 9-1 GCSE

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Chemistry Paper 1 - All Topics

- Atom Models

The model of atoms change quite a lot over time. Rutherford was responsible for discovering the nucleus and the protons. Chadwick discovered neutrons. Bohr discovered/developed our current model.

An atom is made up of protons, neutrons and electrons. Protons are in the nucleus and have a charge of +1 and a mass of 1. Neutrons are in the nucleus also and have no charge and a mass of 1. Electrons are found in the outer shells of an atom, they have a charge of -1 and a mass of 1/1835 (negligible). An elements atomic number tells you how many protons and electrons are in an element. The atomic mass tell you the mass of the element. You can work out the number of neutrons in an element by doing: atomic mass - atomic number.

- Abundance

The equation for abundance is:

( (Mr x %abundance) + (Mr x %abundance) ) / 100

- The Periodic Table

The first attempt of the periodic table was by Newland. He arranged them by mass but didn't leave any gaps. It didn't really work. Mendeleev had a go next. He also arranged things by mass, but left gaps in his. Because he arranged things in groups with similar patterns, and he left gaps, he could predict properties of undiscovered elements.

Groups: Groups tell us the number of electrons in the outer shell of an electron.

Periods: Periods relate to the number of shells an electron has

We can use this information to figure out the electronic configuration of an element. The pattern is 2,8,8,18.

Metals are going to lose electrons, meaning they will have positive charges. Non-metals will gain electrons therefore they have a negative charge, Elements in group 1 will lose 1 electron and elements in group 7 are going to gain 1 electron.

- Ionic Bonding

Ionic bonding is the transfer of electrons from a metal to a non-metal. Anything is group 1 is going to form a +1 ion, group 6 a -2 ion. In order to bond the charges have to be balanced. Therefore if an element has a charge of +3, and the other has a charge of -2, you will need 2(+3) and 3(+2).

The structure is a giant ionic lattice. They have high melting and boiling points, and can only conduct electricity if its molten or dissolved in solution (aq). This is because the ions need to be free to move.

- Covalent Bonding

Covalent bonding is the sharing of electrons between 2 non-metals. For each of these compounds you need to be able to name them, draw them with lines and in a dot and cross diagram and give their formula: hydrochloric acid (HCl), ammonia (NH3), methane (CH4), hydrogen (H2), chlorine (Cl2), oxygen (O2), and nitrogren (N2).

Also need to learn the formula for these compounds: carbon dioxide, water, oxygen gas, hydrogen gas, nitrogen gas, ammonia, hydrochloric acid and sulfuric acid.

The structure of these are covalent