ELECTRONIC CONFIGURATIONS AND THE PERIODIC TABLE

The electronic configuration of an element is related to its position on the periodic table.

the number of circles in the electronic configuration of an element is represented in the periodic table as the period number that element is situated in
the number of electrons in the outermost shell of an element is represented in the periodic table as the group number that element is situated in
the number of electrons in all shells of an element is represented in the periodic table as the element's atomic number

The electronic configuration of sodium  shows that sodium, Na:

  • is in period 3
  • is in group 1
  • has an atomic number of (2 + 8 + 1) = 11

Electronic configurations and properties of elements

The electronic configurations of atoms help explain the properties of elements and the structure of the periodic table. When atoms collide and react, it is the outer electrons that meet and interact. So, elements in the same group have similar chemical properties because they have the same number of electrons in their outer shell.

The electronic configurations of the elements in group 1:

The atoms of all group 1 elements have similar chemical properties and reactions because they all have one electron in their outer shell. Similarly, the atoms of all group 7 elements have similar chemical properties and reactions to each other because all of them have seven electrons in their outer shell.

Groups
The long form of periodic table also consists of the vertical rows called groups. There are in all 18 groups in the periodic table. Unlike Mendeleev periodic table, each group is an independent group.

Characteristics of groups:
(i) All the elements present in a group have same general electronic configuration of the atoms.
(ii) The elements in a group are separated by definite gaps of atomic numbers (2, 8, 8,18, 18,32).
(iii) The atomic sizes of the elements in group increase down the group due to increase the number of shells.
(iv) The physical properties of the elements such as m.p., b.p. density, solubility etc., follow a systematic pattern.
(v) The elements in each group have generally similar chemical properties.