Electron configuration

• Energy levels are the fixed energies that an electron can have, energy levels get closer together as you move further away from the nucleus. Each energy level may be divided into sub-shells.
• The first ionisation energy is the energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of single positive charge gaseous ions.
• Successive ionisation gives the first, second, third, fourth...etc ionisation energies, only one mole of electrons is removed with each ionisation.
• Patterns of ionisation energy:

  • First ionisation energy decreases down a group.

  Atomic radius increases → Shielding increases → Less attraction between electron and nucleus → Less energy required

  • First ionisation energy increases across a period.

  Atomic radius decreases → Nuclear change increases → More energy required
• First ionisation energy abnormalities, such as aluminium, provide evidence for electron configuration in subshells and in shells.

  • Aluminum has a lower expected ionisation energy.
  • Due to the division of energy levels into subshells.
  • Electron configuration: 1s2, 2s2, 2p6, 3s1, 3p1
  • The 3p1 electron is further away from the nucleus and has additional shielding, meaning less attraction, making it easier to remove (less energy required).
• First ionisation energy , such as Be-Ba, provide evidence for electron configuration in subshells and in shells.

  • First ionisation energy shows a general increase across a period.
  • This is due to the atomic number increasing, meaning less attraction to the nucleus, meaning it is easier to remove (=less energy required).