Explanation:
Periods and groups describes the arrangement of elements on the periodic table using the atomic number of each of the given elements.
- Elements having the same number of electrons in the outermost shell of their atoms are placed over one another in vertical columns.
- Each of the resulting vertical column is the group or family.
- The resulting horizontal row is known as the periods.
Elements in the same period have the same number of energy levels or electronic shell.
The period of an element is an indicator of the energy levels in an atom. The groups precisely tells us the number of valence electrons in the atom.
