Question

The atomic number of an element is 20. In the modern periodic table this element
belongs to the period
A 4
B. 8
C. 2
D. 3​

Answer 1

Answer:

A. 4

Explanation:

atomic no. 20 is calcium

Answer 2

Answer:

A] 4th period

Explanation:

In order to answer this question first, we shall write the electronic configuration of the given atomic number.

Electronic Configuration gives a clear idea about the number of electrons present in each orbital of an atom.

The series for writing the Electronic Configuration of elements upto 20 is as follows:

• The first shell or K shell holds 2 electrons
• The second shell or L shell holds a maximum of 8 electrons
• The third shell or M shell holds a maximum of 8 electrons
• The fourth shell or N shell holds a maximum of 2 electrons.

Depending upon the atomic number, the number of electrons in each shell can be easily found out.

Since the atomic number of the given element is 20, its Electronic Configuration can be given as:

2, 8, 8, 2

Here, as it can be observed from Electronic Configuration there are 4 orbitals.

So, the given element belongs to the Fourth period