Question

In which period of the periodic table, an element with atomic number 20 is placed?(a) 4 (b) 3 (c) 2 (d) 1

Answer 1

Answer:

4th period

Explanation:

ca atomic number=20

Answer 2

Answer:

An element with ‘atomic number’ 20 is belongs to 4th period.

Explanation:

• An element with an atomic number is 20, the electronic configuration is$1 s^{2} 2 s^{2} 3 s^{2} 3 p^{6} 4 s^{2}$.
• The last electron means differentiate electron is enters into the fourth orbital. It is indicates the period number.

• The “outer electronic configuration state” is$4 s^{2}$, therefore the period number is four.
• Hence, the period number of an element have 20 is placed in the ‘fourth period’ of the ‘periodic table’.