Chemistry Paper 1

• Dalton 1808- Arranged by atomic weight
• Wolfgang Doberner 1817 -Law of triads is where the middle element is roughly the average of other two elements.
• John Newlands - Law of octaves. He noticed when elements placed in of their atomiv weight there were sometimes similarities between every 8th element.
• Mendeleev arranged his periodic table based on increasing atomic mass, but he left gaps to fit known elements into it's correct place. This was called Mendeleev’s Periodic Table (1869)
• The modern periodic table has seven periods with rows containing metals at the bottom and nonmetals at the top. It also contains groups with columns containing noble gases at the far right hand side.
• Dalton- suggested everything was made of spheres that could not be broken down
• JJ Thompson- discovered the electron which lead to the plum pudding model. Atom is a ball of positive charge with negative elctrons embedded in it.
• Rutrherford- the gold foil experiment to develop the nuclear model
• Bohr- electrons orbit the nucleus in shells of fixed distance from the nucleus
• Chadwick- 1932, discovered neutrons, discovered that the nucleus was made up of protons and neutrons
• Alkali Metals with water: Metal + water -> Metal hydroxide + hydrogen
• 2Li + 2 H20 ---> H2 + 2LiOH
• metal + oxygen ----> metaloxide
• Halogens displacement: If halogen is more reactive then it will displace the other and bond with the metal.
• Noble Gases: are unreactive, full outer shell, as you go down boiling and melting point increase
• Group 1: Get more reactive as you go down because electrons are further away from nucleus. The forces get weak so lower boiling point as not much energy is needed to break forces.
• Group 7: Halogens (alkali metals) - Form ions with a +1 charge
• Group 7: Become less reactive as they go done because its harder to gain an electron as the the outer shell is further from nucleus