1.14 deduce the electronic configurations of the first 20 elements from their positions in the Periodic Table

The first shell always has 2 electrons, and then on the shells can contain a maximum of 8 electrons.

In the periodic table, the row that an element is in corresponds to the amount of shells it has etc. row 3 has three orbiting shells.

Also the group that the element is in corresponds to the amount of electrons in its outer shells etc. group 3 has three electrons in its outer most shell.

An example:

Sulfur is in Group 6 Row 3 and hence it has two shells and six electrons in its outer most shell, making its electronic configuration 2.8.6