Ionisation Energy across a Period

• What should you be able to do by the end of the video?

  Describe and explain ionization energy trends
• How does the first ionization energy vary across period two?

  It generally increases with atomic number
• What does the atomic number indicate?

  Number of protons in an atom
• What happens to the first ionization energy in period two?

  It tends to increase across the period
• What are the exceptions to the trend in first ionization energy in period two?

  Decreases from boron to oxygen
• Why does the first ionization energy generally increase across a period?

  Nuclear charge increases, attracting electrons more
• What happens to the atomic radius as we move across a period?

  It decreases across the period
• What effect does increased nuclear charge have on ionization energy?

  It increases the attraction to outer electrons
• What is similar about the electron shell from which electrons are removed in period two elements?

  Electrons are removed from the same shell
• What subshell do lithium and beryllium have their outer electrons in?

  2s subshell
• Why does boron have a lower first ionization energy than beryllium?

  2p subshell has higher energy than 2s
• What happens to the first ionization energy from carbon to nitrogen?

  It continues to increase
• Why does the first ionization energy decrease from nitrogen to oxygen?

  Electron repulsion in paired orbitals lowers energy
• What pattern is observed in period 3 regarding first ionization energy?

  General increase with exceptions
• What are the exceptions in period 3 for first ionization energy?

  Decreases from magnesium to aluminium
• What energy level do we look at in period 3?

  The third energy level
• What are the key factors affecting first ionization energy across a period?

  • Increasing nuclear charge
  • Decreasing atomic radius
  • Similar shielding effect
• How do the electron configurations of nitrogen and oxygen explain their ionization energy difference?

  • Nitrogen: Separate 2p orbitals
  • Oxygen: Paired electrons in an orbital
  • Repulsion in oxygen lowers ionization energy