chemistry paper 1 grade 9-1

Topic 1- Atomic structure and the periodic table

atoms

nucleus: middle of atom, contains protons and neutrons and has a positive charge

electrons: move around in nucleus, they are negatively charges and have almost no mass

particle            relative mass          relative charge

proton                      1                                +1

neutron                    1                                  0

electron              very small                        -1

atomic number= number of protons

mass number= no. of protons + no. of neutrons

number of neutrons = mass number - atomic number

elements

-a element is a substance made up of atoms that all have the same number of protons in their nucleus

- they can be represented by symbols

-isotopes are atoms with the same number of protons but different number od neutrons

- isotopes  have the same atomic number but different mass number

compounds

- when 2 element atoms join together and form compounds

-represented by formulas

history of the atom

- scientist called Thompson discovered the particle electron in the year 1897(plum pudding model)

-plum model theory showes a ball of + charge with electrons scattered in the ball, his theory was proved wrong by a experiment involved a sheet of gold and charged alpha particles

- Then lead to a scientist called ernest rutherford in 1932 who discovered the proton which led scientist to make a nuclear model of the atom

-Scientist niels bohr changed the nuclear model of the atom, he suggested that electrons orbit the nucleus and each shell is a fixed distance from the nucleus. his theory was supported by many experiements which proved his theory correct.

electronic structure

-  electrons move in shells known as energy levels

- 1st shell can only have 2, 2nd cell can only have 8 and the 3rd shell can only have 8

metals and non- metals

metals: strong,make up majority of the Ph table, great at conducting heat and electricity and have high melting and boiling points

non- metals: tend to look dull, they're brittle, they don't conduct electricity and have low density

group 1 elements

-elements in group 1 are known as alkali metals

- alkali metals form ionic compound with non-metal they are also very soft and have low density

-as you go down down group 1 the melting and boiling points become lower, the relative atomic mass goes up and the reactivity increases

-they all have 1 electron in their outer shell which makes them very reactive

group 7 elements

- when they react they share their electrons and form convelant bonds

-elements in group 7 are known as halogens and all have 7…