atomic structure ✩

• neutral atoms have equal numbers of protons, neutrons and electrons
• the number of protons is the same as the number of electrons
• isotopes are different forms of an element with the same number of protons but different numbers of neutrons
• the mass number is the sum of the number of protons and neutrons
• atom

  the smallest part of an element that can exist. all substances are made up of atoms
• alkali metals

  the elements in Group 1 of their periodic table
• atomic nucleus

  positively charged object composed of protons and neutrons at the centre of every atom with one or more electrons orbiting it
• atomic number

  the number of protons in the nucleus
• chromatography

  a separation technique used to separate a mixture of chemicals by distributing the components between two phrases
• compound

  a substance made up of two or more types of atoms chemically combined together
• crystallisation

  a separation technique used to produce solid crystals from a solution by evaporating the solvent
• displacement


  a chemical reaction in which a more reactive element replaces a less reactive element from its compound
• electron

  negatively charged subatomic particles which orbit the nucleus at various energy levels. very small relative mass (negligible).
• electron shell

  diffferent energy levels in atoms occupied by electrons
• element 


  a substance made up of only one type of atom
• filtration

  a separation technique used to separate solids from liquids
• fractional distillation

  a method of separating a mixture of substances according to their different boiling points
• group (periodic table)

  the columns of the periodic table represent different groups of elements. elements with similar properties are in the same group.
• halogens

  the elements in Group 7 of the periodic table
• ion

  an atoms or molecule with an electric charge due to the loos or gain of electrons
• isotope

  atoms of the same element with the same number of protons but a different number of neutrons
• mass number

  the total number of protons and neutrons in the nucleus
• metals

  elements that react to form positive ions. found to the left and towards the bottom of the periodic table
• mixture

  a mixture consists of two or more elements or compounds not chemically combined together
• neutron

  neutral subatomic particle present in the nucleus of the atom. relative mass of 1.
• noble gases

  the elements in Group 0 of the periodic table
• non-metals

  elements that react to form negative ions. found towards the right and top of the periodic table.
• nuclear model

  the nuclear atomic model stated that the mass was concentrated at the centre of the atom and that the nucleus was charged
• periodic table

  table of elements, arranged in order of atomic number and such that elements with similar properties are in the same column (group)
• plum pudding model

  atomic model devised after the discovery of the electron. the model suggests the atom is a ball of positive charge with negative electrons scattered through it.
• proton

  positively charged subatomic particle present in the nucleus of the atom. relative mass of 1
• relative atomic mass


  an average value that takes account of the abundance of the isotopes of the element
• simple distillation

  a procedure by which two liquids with different boiling points can be separated
• transition metals

  the collection of metallic elements in the middle of the period table
• Compound

  Contains two or more different elements chemically combined in fixed proportions
• Compounds usually have totally different properties to the elements that they're made from
• Mixture

  Contains different elements or compounds, but they are not chemically combined
• Mixtures can be separated using physical separation techniques
• Physical separation techniques

  • Filtration
  • Distillation
  • Crystallisation
  • Chromatography
• Molecule

  Any elements chemically combined, even if they are the same element