atomic structure and the periodic table

• All substances are made of atoms
• An atom is the smallest part of an element that can exist on its own
• Atoms have three main parts - protons, neutrons and electrons
• An element is a substance that contains only one sort of atom
• A compound is a substance containing two or more different elements chemically combined together
• The mass number tells us how many protons and neutrons there are in the nucleus
• Isotopes are atoms with the same number of protons but different numbers of neutrons
• Ions are charged particles formed when atoms lose or gain electrons
• Anions are negatively charged ions (gain electrons)
• Cations are positively charged because they have lost electrons
• Metals tend to form cations because they lose electrons easily
• Group 0 - noble gases
• Group 0 elements are called noble gases, they don't react as they already have full outer shells
• Group 8 - noble gases
• Elements in group 7 are very reactive due to their lack of electrons in their outer shells
• Alkali metals (group 1) are highly reactive with water and oxygen
• The further right an element is on the periodic table, the more reactive it will be
• Alkali metals (group 1) are soft, malleable and ductile
• A mixture is a substance that contains two or more elements or compounds that are not chemically combined
• Filtration is used to separate a solid from a liquid.
• Crystallisation is used to separate a soluble solid from a solution.
• Fractional distillation is used to separate a mixture of liquids by boiling points
• Simple distillation is used to separate a solvent from a solution.
• Chromatography is used to separate mixtures containing different coloured substances.
• The periodic table was discovered by Dmitri Mendeleev in 1869.
• Mendeleev left gaps on his periodic table, which were later filled with undiscovered elements.
• Elements are arranged in groups based on their properties.
• Groups have similar chemical properties due to having the same number of electrons in their outer shell.
• Group 7

  Halogens
• Group 1

  Alkali metals
• Group 0


  Noble gasses
• Transition metals are good catalysts because they have high melting points and high boiling points
• Transition metals can form ions with different charges
• The reactivity series is used to predict which metal will displace another from its compound
• A more reactive metal will displace a less reactive one from its compound
• Strong acids completely ionise in solution while weak acids only partially ionise
• The electron configuration is the arrangement of electrons in an atoms shells