Chemistry

• The periodic table shows the elements arranged by increasing atomic number, which is the number of protons in an atom's nucleus.
• Elements are grouped into families or groups based on their properties.
• An element is A substance that is made of only one sort of atom
• A compound is A substance formed from two or more different elements chemically combined together
• Atomic mass - The average relative mass of all atoms of an element
• A compound is a substance made up of two or more different elements chemically combined.
• The size of an atom is 1x10^-10 m.
• A mixture is a substance that contains two or more elements or compounds that are not chemically combined.
• A Atom is the smallest particle of a chemical element that can exist.
• An insoluble substance is a substance that cannot be dissolved in water.
• Filtration is used to separate a insoluble solid from a liquid.
• A Solute is a substance that can dissolve in a solvent.
• A solvent is a liquid that can dissolve a substance. eg water , alcohol.
• Evaporation is a process used To separate a soluble solid from a liquid.
• Distillation is a process used to separate 2 liquids with different boiling points.
• A pure substance is a single element or compound that is not mixed with any other substances.
• A pure substance is a substance that has had nothing added to it or taken away from it.
• A Formulation is a mixture that has been designed to have a specific purpose.
• Crystallisation is the process of forming solid crystals from a solution by allowing the solvent to evaporate slowly.
• Chromatography is a method used to separate mixtures of substances and identify the substances in the mixture.
• The smaller number is the atomic number , this is the number of protons.
• On the periodic table The number of neutrons is the

  atomic mass- the atomic number
• The number of protons is equal to the number of electrons.
• Protons have a relative mass of 1.
• Neutrons have the relative mass of 1.
• Electrons have the relative mass of 0.0005
• Protons have the relative charge of +1
• Electrons have the relative charge of -1
• Neutrons have the relative charge of 0
• In their first shell atoms have space for 2 electrons.
• The second shell can hold up to 8 electrons.
• Atoms with full outer shells are more stable than those without, so they tend not to react chemically.
• When drawing a diagram of an atoms shell go from the middle and fill shells outwards until you don’t have any electrons left.
• You can see how many shells a atom should have by looking at the period number
• You can see how many electrons there would be on the outer shell by looking at what group the element is in.
• Distillation is used to Separate 2 liquids that have different boiling points
• Impure substances have a high boiling point and a low melting point . And a range of temperatures for the melting point and the boiling point.
• Rf= distance travelled by substance / distance travelled by solvent
• Alkali metals get more reactive as they go DOWN the group. They also need to lose 1 electron.
• Noble gases are stable and are not reactive and they have a full outer shell of electrons.