periodic table

• Periodic table


  An organisational tool to identify patterns and trends in, and relationships between, the structures (electronic configurations and atomic radii) and properties (electronegativity, first ionisation energy, metallic or non-metallic character and reactivity) of elements
• Key knowledge from the study design

  • For each trend of the periodic table, you need to be able to give a definition, state the trend and explain why it increases/decreases up/down a group and period
• Features of the periodic table


  • Arranged in order of increasing atomic number (number of protons of an element)
  • Periods (horizontal rows 1-7)
  • Groups (vertical columns 1-18)
  • Gives information about the electron configuration
  • Arranged in order of increasing valence electrons (electrons in outer shell)
  • Each element in the same period has the same number of electron shells
  • Each element on the same group has the same number of valence electrons in their outer shell
• Tip: when working out valence e- in group 13 to 18, subtract 10
• Periodic table blocks


  • s-block (Group 1 + 2 and He)
  • p-block (Groups 13-18 except He)
  • d-block (Groups 3-12)
  • f-block (Lanthanoids and Actinoids)
• Highest energy subshell configurations

  1. block: s1 or s2
  2. block: s2 p1 to s2 p6
  3. block: d1 s2 to d10 s2
  4. block: 4f subshell - Lanthanoids, 5f subshell - Actinoids
• Periodic table groups


  • Noble gases
  • Halogens
  • Non-metals
  • Alkali metals
  • Alkali Earth metals
  • Transition metals
  • Other metals
• Core charge


  Measure of the attractive force felt by the valence electrons in the outer shell towards the nucleus
• Determining core charge


  Core charge = number of protons - number of inner shell electrons
• Determining core charge


  • Aluminium: Protons = 13, Inner shell electrons = 10, Core charge = 13 - 10 = +3

  Sodium (group 1): Protons = 11, Inner shell electrons = 10, Core charge = 11 - 10 = +1

  Chlorine (group 17): Protons = 17, Inner shell electrons = 10, Core charge = 17 - 10 = +7
• Atomic size


  • Decreases across a period (electrons being added to same energy level, protons being added to nucleus, valence electrons pulled closer)

  Increases down a group (number of occupied energy levels/shells increasing)
• Electronegativity


  Ability of an atom to attract electrons to itself
• Electronegativity trends


  • Increases across a period (more protons in nucleus)

  Atoms on the right are close to filling their valence outer shells therefore electronegativity increases
• Atomic radius


  Distance from the nucleus to the outermost electron shell
• Atomic radius trends


  • Increases down a group (increase in number of electron shells)

  Decreases across a period (valence shell pulled closer to nucleus)
• The more electrons (-) and protons (+), the larger the atomic radius
• First ionisation energy


  Energy required to remove the first valence electron from an atom
• Ionisation energy trends


  • Decreases down a group (electron to be removed is increasingly distant from nucleus)

  Increases across a period (more protons being added to nuclei, electrons more tightly held)
• The further away an electron is from the nucleus, the easier it is to pull away. The lower the atomic number the higher the ionisation energy.
• Metallic character


  Tendency of an atom to lose an electron instead of gaining an electron in order to fill its valence shell
• Metallic character trends


  • Non-metals (on the right) have more valence electrons therefore the tendency to lose their electrons decreases
• Reactivity of metals


  Measure of how readily an element will react with another element/lose electrons
• Reactivity of non-metals


  Measure of how readily a non-metal atom will accept an electron
• Atoms of non-metallic elements undergo chemical reactions to gain electrons to form a stable outer shell (octet arrangement)