The long form of periodic table consist of vertical columns called groups and horizontal rows called periods.
Elements are arranged in the increasing order of atomic numbers.
Elements in the modern periodic table are arranged in 7 periods and 18 groups.
Horizontal rows are called periods and vertical columns are called groups.
Elements are placed in periods based on the number of shells in their atoms.
The shortest period is the first period which contains only two elements – Hydrogen and Helium.
Sixth period is considered as the longest periods in the periodic table. It contains elements from Cesium to Radon.
Seventh period is incomplete period.
In periodic table Lanthanides and Actinides are shown in the bottom of the periodic table