Atomic Structure

Atomic Structure

1. Trends

   • Ionisation Energy
     • The energy required to remove an electron from each of a mole of a gaseous atom
     • Down a group
       • Decreases
         • Very little change to nuclear charge, large increase in electron shielding and atomic radius
     • Across a period
       • Increases
         • Increase in nuclear charge, small increase in electron shielding and atomic radius
   • Electron Affinity
     • The energy change upon addition of an electron to each of a mole of a gaseous atom

2. Electron Configuration

   • Subshells
     • A category of electrons within a shell that is in the same type of orbital
   • Orbitals
     • A category of electrons within a shell that is in the same type of orbital
     • Electrons orbit the nucleus in a random sphere
     • First Shell
       • 1 s orbital (2 electrons)
     • Second Shell
       • One s orbital (2 electrons)
       • Three p orbitals (6 electrons)
         • Total 8 electrons
     • Third Shell
       • One s, three p and 5 d orbitals (18 electrons)
   • Notation
     • You can note the electron subshells with all the subshells written in
       • e.g (Na) - 1s2 2s2 2p6 3s1
     • This can be shortened by adding the nearest noble gas
       • e.g. (Na) - [Ne] 3s1

3. Emission Spectra

   • Atomic Absorption Spectroscopy
     • Shows all colours of light except those which can be absorbed by atoms of that element
       • AAS involves passing electromagnetic radiation (white light) through a sample and observing the pattern of lines
   • Balmer Series
     • Electron Shells
       • Niels Bohr discovered that this pattern of lines can be explained with electrons of light at energy levels
       • Inputs of energy can exile electrons which can move into higher energy levels
       • When electrons relapse, they emit photons of light, each with a different energy
         • Electrons can relapse in more than one way - i.e. via other shells, which results in more photons of light being emitted
     • He observed the visible region of the emission spectra

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