Question

An element has 20 electrons and 20 neutrons. It is electrically neutral. State the following-

a) The Atomic number of the element is?

b) The Mass number of the element is?

c) Draw the atomic structure of the element.

Answer 1

a)

• In an electrically neutral atom, the number of protons and the number of electrons will be equal.
• Here it has given that the number of electrons is 20 hence the number of protons will be also 20.
• The atomic number is the number of protons in an atom. Thus atomic number = 20.

b)

• The mass number is the sum of the number of protons and the number of neutrons in an atom.
• Hence mass number=(20+20)=40.

c) Element with atomic number 20 is calcium.