electron) into 3s level. Therefore ‘Na’ is an s-block element. Aluminium (Al) gets its differentiating electron into ‘p’ subshell and it is a p-block element. Scandium (Sc) gets its differentiating electron into ‘d’ subshell. Therefore it is a d-block element. Cerium (Ce) gets its new coming electron into ‘f’ subshell, hence,it is an f-block element.

    Let us observe the electronic configurations of the following elements.
The last coming electron is underlined.

₁₁Na  1s² 2s² 2p⁶3s¹
₁₃Al   1s² 2s²2p⁶3s²3p¹
₂₁Sc  1s²2s² 2p⁶ 3s²3p⁶ 4s² 3d¹
₅₈Ce 1s²2s² 2p⁶3s²3p⁶ 4s²3d¹⁰ 4p⁶ 5s² 4d¹⁰5p⁶ 6s² 5d¹ 4f²

The vertical columns in the periodic table are known as groups. There are eighteen groups in long form of periodic table. They are represented by using Roman numeral I through VIII with letters A and B in traditional notation.

    According to latest recommendation of the IUPAC, these groups are represented by Arabic numerals 1 through 18 with no A and B designations.

    We use the latest system with the traditional heading following in parenthesis.

Eg: Group 2 (II A); Group 16 (VI A)

    Group of elements is also called element family or chemical family.

    For example Group 1 (IA) has from Li to Fr with outer shell electronic configuration ns1 and is called Alkali metal family.

Some main group elements of s-block and p-block have family names as given in the following table.

    Observe the long form of the periodic table and complete the table with proper information.