Question

What are the main features of the modern periodic theory?

Answer 1

The main features of modern periodic table

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.