The periodic table

• What does the periodic table show?

  All known elements in order of atomic number
• What do periods in the periodic table indicate?

  Number of main energy levels of elements
• What do groups 1 to 0 indicate in the periodic table?

  Number of electrons in outer energy level
• What does the s block in the periodic table represent?

  Elements with electrons in the s sub-level
• What does the p block in the periodic table represent?

  Elements with electrons in the p sub-level
• What does the d block in the periodic table represent?

  Elements with electrons in the d sub-level
• What is the first ionisation energy?

  Energy to remove an electron from an atom
• What does the equation M(g) + e represent?

  Ionisation of an atom in gaseous state
• What does a large increase in successive ionisation energies indicate?

  Evidence for main energy levels (quantum shells)
• What happens to first ionisation energy down a group?

  It decreases as you descend the group
• Why does first ionisation energy decrease down a group?

  Outer electron is further from the nucleus
• What is the first ionisation energy of lithium?

  520 kJ/mol
• What is the first ionisation energy of sodium?

  495 kJ/mol
• What is the first ionisation energy of potassium?

  420 kJ/mol
• What is the general trend of ionisation energy across a period?

  It increases across the period
• Why does ionisation energy increase across a period?

  Nuclear charge increases while shielding stays the same
• What are the anomalies in ionisation energy trends?

  Group 3 and Group 6 show exceptions
• What is the first electron affinity?

  Energy change when an electron is added
• What is the nature of the first electron affinity process?

  It is an exothermic process
• What does the equation X(g) + e represent?

  Electron affinity of an atom in gaseous state
• What happens to first electron affinity down a group?

  It decreases as you descend the group
• Why do successive electron affinities become endothermic?

  Electron is added to a negative ion causing repulsion
• Why does first electron affinity decrease down a group?

  Shell is further from the nucleus with more shielding
• What are the trends in ionisation energy and electron affinity across periods and down groups?

  • Ionisation energy increases across a period
  • Ionisation energy decreases down a group
  • First electron affinity decreases down a group
  • First electron affinity generally increases across a period
• What are the key factors affecting ionisation energy and electron affinity?

  • Nuclear charge
  • Distance from nucleus
  • Shielding effect
  • Subshell occupancy