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1. >atomic number = number of protons in a nucleus of an tom of that element.> Relative atomic mass = the weighted average mass of an atom of that element divided by 1/12th mass of a carbon 12 atom.> Mass number of an isotope of an element= sum of the number of protons and neutrons in the nucleus.> relative molecular mass of an element/compaound= the av mass of a molecule of that divided ny 1/12th mass of carbon 12 atom.

2. Mass spectometry - 1. Vaporisation, using an electric heater. 2. Ionisation gas particles are bombarded with high energy electrons = positive ions. 3. Acceleration- positive ions are accelerated by an elec field. 4. Felection = paths are altered by a magnetic field. Lighter ions have less momentum so are deflected more. 5. Detection = magnetic field strength slowly increases this changes the mass/charge ratio of ions which can reach the detector. Mass spectrum is produced.

3. Electronic structure = electron shells are made up of subshells (S, P +D) and orbitals.

   • Chromium and copper will donate 1 of their 4S electrons to 3d subshell as more stable with full/ half full 4s
   • IONISATION ENERGIES = the energy neededremove 1 electron from each atom in 1 mole of gaseous atoms to form 1 moe of gaseous 1+ ions
     • FACTORS = 1. Nuclear charge - more protons there are in the nucleus the more positively charged the nucleus is and stronger attraction to electrons. 2.Distance - attraction decreases with distance. 3. Shielding = as no. of elecs between outer elecs and nucleus.
       • TRENDS
         • First ionisation energy of elements down a group decreases. As charge remains same but more distnace and shielding so less attraction.
         • First ionisation energy increases across a period as nuclear charge increases so there is more attraction between elections and nuclei.
           • Exceptions== Drops between group 2 Be and 3 B - Berylliums outer elec is in 2s subshells, Borons is in 2p subshell. 2p has higher energy so slightly further away so not as much attraction. same with Mg and Al. == Drops between groups 5+6 > electron repulsion. 2 p subshell has 3 orbitals , N has 1 in each whereas O has 2 in one so repel = easier to lose one.