b. Structure of the modern periodic table
1. The modern periodic table consists of 7 horizontal rows called the periods and 18 vertical columns called the groups.
2. Apart from these seven rows, two rows are shown separately at the bottom of the periodic table. These are called lanthanide series and actinide series respectively.
3. The entire periodic table is divided into four blocks:
4. A zig - zag line is drawn in the p - block of the periodic table. Metals lie on the left side while nonmetals lie on the right side of this zig - zag line. Metalloids lie along the border of this line.