Any chemical element (X) can be represented asZXA where ‘Z’ is an atomic number and ‘A’ is the mass number. The Atomic number refers to the number of protons and the mass number refers to the sum of protons and neutrons in an atom. For an element, calcium which has 20 protons and 20 neutrons, identify the correct representation:
The correct option is D 20Ca40
The mass number of an atom is the sum of protons (p) and neutrons (n). Given, calcium has 20 protons and 20 neutrons.
So, mass number (A) of Calcium = p + n = 20 + 20 = 40. Hence, A = 40.
Atomic number is the number of protons. It is given as 20.
So, ZXA for Calcium is 20Ca40.