CHEMISTRY GCSE

• compound- two or more elements chemically combined
• ionic compound —> metal + non metal
• mixture- two or more elements or compounds not chemically bonded together
• filtration- to separate an insoluble solid from a liquid
• crystallization- to separate a soluble solid from a solution
• distillation- to separate liquids with different boiling points
• Simple distillation- 2 liquids
• fractional distillation- multiple liquids in a fractionating column
• chromatography- mixtures of liquids seperated by their retention
• chromatography paper- stationary phase
• solvent- mobile phase
• proton nucleus, relative mass of 1 relative charge of +1
• electron on shell, very small relative mass, charge -1
• neutron in nucleus relative mass, 1 relative charge 0
• radius 1x10^-10
• nucleus 1x10^-14
• Isotopes- an element with the same number of protons and electrons but a different number of neutrons
• chlorine 35 (75%) 37 (25%)
• john dalton, jj thompson, rutherford and marsden/geiger, neils bohr, protons (1920), james chadwick
• periodic table- groups and periods (horizontal same number of shells)
• metals on the left non metals on the right
• metals- positive ions, malleable, high mp, conductive
• periodic table —> firstly ordered by atomic weight (elements didnt fit), incomplete table
• Mendeleev —> switched some elements, left gaps for new elements, made predictions for the elements that will be discovered (later did fit)
• group 1- alkali
• group 7- halogen
• group 0- noble gases
• alkali metals- soft, highly reactive, one outer shell electron, positive ions
• metal + oxygen—> metal oxide
• metal + water —> metal hydroxide +hydrogen
• metal + chlorine —> metal chloride
• halogens—> fluorine, chlorine, bromine, iodine, astatine
• halogens- divalent molecules with 2 molecules, 7 electrons on outer shell, non metals, covalent bonding, gain electron to react
• halogens— more reactive up the group elements get smaller
• group 1– increasing reactivity down the group, more stable, more reactive, more easily ionised
• fluorine and chlorine are gases
• bromine liquid
• iodine and astatine is a solid
• group 0 noble gases— unreactive, have a full outer shell, dont usually form compounds, can be useful to stop chemical reactions happening, down the group the atoms become larger, stoner force, harder to overcome, more energy required, higher bp down the group
• transition metals—> comparison group 1, harder, denser, high mp, less reactive, forms ions with different charges, catalysts, coloured compounds