Periodicity

The Periodic Table

The Periodic Table

The periodic table consists of all the elements known to man. The elements are arranged in order of atomic number from 1 to 106. They are also arranged so that atoms

The rows represent the elements in terms of shell number, with those composed of one shell in the first row and those with increasingly more shells placed underneath. A row of elements arranged like this is called a period.with the same number of shells and atoms with similar electronic configurations are put together.

  • The elements are also arranged in columns. These elements share similar electronic configurations. A column of elements arranged like this is called a group.

As you can see from the table, H and He do not fit well into any group. Instead, He is compared in terms of the physical and chemical properties it shares with other elements and is placed in group 0. H, on the other hand, is all by itself as it does not behave like any other element.

Ce-Lu and Th-Lw tend to be placed below the other elements in order to save enough space for groups VI and VII on a sheet of A4.

The elements belong in one of four main blocks

  • The s-block: elements with an outer shells that contains only s electrons.
  • The p-block: elements that have at least one p-electron in their outer shell.
  • The d-block: elements that have in their outer shell at least one d-electron and s-electron but no f or p electrons.
  • The f-block: elements that have in their outer shell at least one f-electron and s-electron but no d or p electrons.

Elements that are part of the same group share similar properties. As a period is crossed, the properties of the elements change.

With an increase in atomic number, the elements exhibit trends that are present in each period. These trends are called periodic trends.