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.