Which of the following statements is NOT correct with reference to the modern periodic table?

Correct option is A

The correct answer is: (a) The first period contains 8 elements.

Explanation:

• The first period of the modern periodic table contains only 2 elements: Hydrogen (H) and Helium (He).

• This is because the first energy shell (K shell) can hold a maximum of 2 electrons.

• Hence, statement (a) is NOT correct.

• Modern Periodic Table is based on increasing atomic number (proposed by Henry Moseley).

• It has 7 periods (horizontal rows) and 18 groups (vertical columns).

• The second and third periods have 8 elements each, filling the 2nd and 3rd energy shells.

• Lanthanoids (Z=57–71) and Actinoids (Z=89–103) are placed separately to maintain the table’s structure.