A level Chemistry

• Atom


  Smallest particle of an element that can exist
• Element


  Substance consisting of atoms which all have the same number of protons
• Electron


  1/2000 that of a proton
• Neutron


  Present in all atomic nuclei except those of ordinary hydrogen
• Isotope 


  Forms of the same element with the same number of protons, but different number of neutrons
• Relative atomic mass (Ar)


  The ratio of the average mean mass of one atom of an element to one twelfth of the mass of an atom of carbon-12
• Cation


  Positive ion
• Anion


  Negative ion
• Dissociate


  When ionic compounds separate into their respective cations and anions when place in water
• Spectator ions


  Appear as themselves on both sides of the equation
• S orbital

  Spherical

  1 orbital

  2 electrons
• P orbital

  3 orbitals

  6 electrons

  Dumbbell shape

  90 degrees to each other
• D orbital


  5 orbitals

  10 electrons

  Clover shaped
• F orbital


  7 orbitals

  14 electrons
• Auf bau principle

  The ground state of an atom or ion, electrons fill the subshells of the lowest available energy
• Ground state


  Lowest possible energy state
• Relative formula mass


  The weighted average mass of a formula unit of a substance relative to 1/12 the mass of an atom of carbon-12