Atomic Structure

Atomic Structure

1. Subatomic Particles

   • Electrons
     • Electron levels have sub levels
       • S sub levels have upto 2 electrons
       • P sub levels have upto 6 electrons
       • D sub levels have unto 10 electrons
       • In each sub level, the electron pairs must be spinning in different directions
       • Anomalies
         • Chromium
           • [Ar] 4s1, 3d5
         • Copper
           • [Ar] 4s1, 3d10
         • Atoms aim to be stable
           • Half full sub levels give more stability in the anomalous cases

2. Atoms

   • Mass number (A)
     • Sum of protons and neutrons
     • Relative masses
       • The mass of an atom relative to the C12 isotope having a value of 12.000
   • Atomic number (Z)
     • Number of protons in the nucleus of an atom
     • Determines what type of atom it is

3. Isotopes

   • Atoms with the same number of protons but a different number of neutrons
   • Properties
     • Chemical: identical
     • Physical: can differ
   • Abundance is used in mass spectrometry to find the average atomic mass of an atom

4. Ionisation Energies

   • First IE
     • The energy required to remove 1 mol of electrons from 1 mol of gaseous atoms to form 1 mol of positive ions
   • The greater the electrostatic attraction, the harder it is to remove the electron
   • Large jumps in successive ionisation energies for an element are due to a change in energy levels
   • IE is lower when there is greater shielding (down a group)
   • First IE for period 2 evidences sub-levels

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