Periodic Trends

Section: Overview of Periodic Trends

  • The Periodic Table is organised in such a way that elements with similar properties align in the same group (column), illustrating periodic trends.
  • Periodic trends occur when elements show patterns in their properties based upon their periods (rows) and groups (columns) in the Periodic Table.
  • These patterns, or trends, demonstrate how certain chemical and physical properties of elements change across periods and down groups.

Section: Atomic Radius

  • The atomic radius (size of the atom) decreases as you move across a period from left to right.
  • This decrease is due to the increase in protons, causing increased nuclear charge, pulling electrons closer to the nucleus.
  • However, as we move down a group, atomic radius increases. This is due to the addition of energy levels (shells), hence more distance from the nucleus.

Section: Ionisation Energy

  • Ionisation energy is the energy required to remove an electron from an atom.
  • It generally increases as you move across a period due to an increase in nuclear charge, making electrons harder to remove.
  • Ionisation energy decreases as you move down a group, because the outer electrons are further from the nucleus and hence less attracted to it.

Section: Electronegativity

  • Electronegativity is a measure of an atom’s ability to attract a bonding pair of electrons.
  • It tends to increase across a period due to the higher nuclear charge, which attracts electrons more strongly.
  • Electronegativity generally decreases down a group as the bonding electrons are further from the nucleus in the additional energy levels (shells).

Section: Metallic and Non-Metallic Character

  • Elements on the left of the Periodic Table are metals, and they tend to lose electrons in reactions, while elements on the right are non-metals, which typically gain electrons.
  • As you move across a period from left to right, metallic character decreases while non-metallic character increases.
  • Metallic character increases down a group while non-metallic character typically decreases.
  • This trend is influenced by the atomic radius, ionisation energy, and electronegativity trends.