Na, Mg, Al, Si, P, S, Cl and Ar belong to the _____ period of the modern periodic table.

Correct option is A

The correct answer is (a) Third.
· Na (Sodium), Mg (Magnesium), Al (Aluminum), Si (Silicon), P (Phosphorus), S (Sulfur), Cl (Chlorine), and Ar (Argon) all belong to the third period of the modern periodic table.
· These elements are arranged based on increasing atomic numbers, starting with sodium (Na) and ending with argon (Ar) in the third period.
Information Booster:
· Third Period: This period consists of elements with atomic numbers ranging from 11 (Sodium) to 18 (Argon).
· Trends: Across the third period, elements transition from metals (e.g., Sodium, Magnesium) to non-metals (e.g., Sulfur, Chlorine) and finally to noble gases (e.g., Argon).
Additional Information:
· Na to Ar: Sodium (Na) and Magnesium (Mg) are metals, whereas Phosphorus (P), Sulfur (S), and Chlorine (Cl) are non-metals. Argon (Ar) is a noble gas.
· Periodic Table Trends: Moving across the period from left to right, there is an increase in electronegativity and ionization energy, while atomic size decreases.