Periodicity - an Introduction
Periodicity is the essence behind the Periodic Table. As the name suggests, the Periodic Table is built up of repeating patterns that conform to certain rules.
For example elements
- Group I (the alkali metals) all have similar chemistry.
- Atomic radii increases across Period 3.
This section of the course essentially looks at three aspects of periodicity.
1. Trends across Period 3
2. Trends in Group II (The Alkali-earth metals)
3. Trends in Group VII (the Halogens)
Classification of elements
Elements are classified according to their position in the Periodic Table.
So elements in the s-block (Magnesium, potassium etc) are conveniently called s-block elements. Interestingly elements in the d-block (Copper, Manganese etc are also named sensibly as d-block elements. The pattern continues with the p- and f- blocks.The elements are named according to which of their electrons have the highest energy
Li (1s2 2s1) and Mg
(1s2 2s2 2p6 3s2) are s
block elements
Cl
(1s2 2s2 2p6 3s2 3p5) is a p block element