Electronic configurations and the periodic table

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

The links are:

  • 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
Electronic configuration featureLink to the periodic table
Number or numbers of circlesPeriod number
Number of electrons in outermost shellGroup number
Total number of electrons in all shellsAtomic number

The electronic configuration of sodium (2.8.1) 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:

Table showing electronic configurations of group 1 elements, lithium, sodium and potassium. Group 1 elements have similar properties and reactions as they all have one electron in their outer shell.

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.

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