what I need to learn

atoms radius=0.1 nanometers

atomic number is how many protons are in the nucleus

mass number is total number of protons and neutrons

relative atomic mass= (isotope abundance x isotope mass number)/ sum of abundances of all isotopes

history of the atom

• dalton- solid spheres that make up different elements
• thompson-measurments of charge and mass  showed they must have electrons, so he made the plum pudding model
• rutherford-alpha particle scattering experiment disproved the plum pudding model. said there was positive in the middle and a cloud of electrons around it
• bohr-rutherford had to be wrong because the atom would collapse. he said they orbited in shells. then he discovered protons
• chadwick-discovered neutrons

elements were categorised in physical and chemical properties and their relative atomic mass

mendeleev- mainly in order of atomic mass. gaps were left so elements with similar properties were in the same group. room for undiscovered elements and he could predict their properties. they were found and proved his thoery.

the discovery of isotopes also proved he was right to consider their properties because they have similar properties but different msses.

groups- how many electrons are in the outer shell. theyre likely to react in a similar way

periods- each new period represents another full shell of electrons

metals form positive ions when they react

transition metals can have more than one ion

down group 1- increased reactivity, lower melting and boiling points, higher relative atomic mass

alkali metal + water= hydrogen and metal hydroxides

alkali metal + chlorine= metal chloride salts

alkali metal + oxygen= a metal oxide

down group 7- less reactive, higher melting and boiling points, higher relative atomic masses

more reactive halogens will displace less reactive halogens

noble gases are inert,monatomic gases and colourless at room temperature

as you go down group 8 the boiling point increases because there are greater intermolecular forces