group 1 & 7

• elements in the same group have the same number of outer shell electrons
• group 1 metals are soft - can be cut using a knife
• group 1 metals become dull as they react with oxygen rapidly to form alkali metal oxides
• group 1 metal have a low density - Li, Na and K can float on water
• group 1 metals have low melting points - Na and K melt from heat generated when reacting with water
• group 1 get softer, more dense, lower B.P as you move down the group
• group 1 metals are very reactive
• group 1 metals all react with oxygen to make metal oxides
• all group 1 metals fizz when they react with water
• Li, Na and K all move around on surface and float until completely dissolved
• group one reactions are exothermic = heat up surroundings and Na and K can melt from heat
• potassium produces a lilac flame
• group 1 elements react by losing their 1 outer shell electron to form metal oxide ions with a +1 charge, the further away from the nucleus the outer shell is (has more shells between) = the easier it is to lose the electron so it is more reactive - this is because the attraction between the negatively charged electron and the nucleus is weaker the further away the electron is
• group 7 elements are molecules made up of pairs of atoms called halogens
• group 7 elements are non-metals and have coloured gases
• Flurine is a pale yellow gas
• Chlorine is a pale green gas
• Iodine is a grey solid and produces a purple vapour when heated
• group 7 elements get less reactive down the group
• group 7 elements are very reactive - have 7 electrons so react by gaining an electron to fill their outer shell, when a halogen atom reacts with a metal, it gains an electron and forms an ion with a 1- charge called a halide ion
• group 7: larger distance between outer shell and nucleus = less reactive
• use displacement reactions to find the order of reactivity of chlorine, bromine and iodine
• a more reactive halogen can displace a less reactive halogen
• in group 7, the nearer the outer shell is to the nucleus = the easier it is to attract an electron so is more reactive at top of group
• Bromine is a orange liquid and produces an orange vapour when heated
• lithium with water (4) = fizzing, lithium moves around on surface, lithium disappears, lithium floats
• sodium with water (5) = fizzing, moves around, melts, disappears, floats
• potassium with water (6) = fizzing, moves around, melts, lilac flame, disappears, floats
• group 1 = alkali metals
• group 7 = halogens
• iodine = dark grey solid
• chlorine = green gas
• astatine = black solid
• fluorine = yellow gas