Question

The atom of an element has 20 protons, 20 electrons, and 20 neutrons :

(a) What is the atomic number of the element?

(b) What is the mass number of the element?

(c) Name the element.

(d) Write the electronic configuration of the element.

Answer 1

Part (a): Atomic number of the element:

• The atomic number of the element is equal to the number of protons present in the nucleus of an atom.
• It is given that the number of protons is equal to 20.
• So, the atomic number of the element is also 20.

Part (b): Mass number of the element:

• The mass number of the element is equal to the sum of the number of protons and the number of neutrons present in the nucleus of an atom.
• It is given that the number of protons and neutrons is equal and is equal to 20.
• So, mass number = number of protons + number of neutrons = 20+20= 40.
• Thus, the mass number of the element is 40.

Part (c): Name of the element:

• The element which is having atomic number 20 is Calcium $\left(\mathrm{Ca}\right)$.

Part (d) Electronic configuration of the element:

• Electronic configuration of $\mathrm{Ca}$ is 2,8,8,2.

Hence,

• The atomic number of the element is 20.
• The mass number of the element is 40.
• The name of the element is Calcium.
• The electronic configuration of Calcium is 2,8,8,2.