Question

The mass number of a nucleus is:
A) Always less than its atomic number
B) Always more than its atomic number
C) Sometimes equal to its atomic number
D) Sometimes more than and sometimes equal to its atomic number

Answer 1

Hint: To solve this question we need to know the basic theory related to the mass number and atomic number. As we know the mass number is also called atomic mass number. and nucleon number is the total number of neutrons and protons as discussed below.

Complete step by step solution:
The mass number depends on the total number of protons and neutrons. A proton is a subatomic particle and its symbol is p. Protons are positive electric charge. Proton was discovered by Ernest Rutherford in 1920 The number of protons in the nucleus is referred to as the atomic number.
For better understanding we consider a nucleus consists of Z protons and N neutrons.
Let the mass of the nucleus be M.
If a nucleus has a simple collection of Z protons as well as N neutrons then the mass of the nucleus would be just the sum of the masses of these constituent nucleons.
The neutron was discovered by James Chadwick in 1932 and the discovery of the neutron and its properties was proved very helpful in the developments in atomic physics. The neutron is slightly heavier than the proton and the charge of the neutron is neutral.
Neutrons and protons together known as nucleons. The mass number and nucleon number are written either after the element name or as a superscript to the left of an element's symbol.

Therefore, from above conclusion the mass number of a nucleus is Sometimes more than and sometimes equal to its atomic number.

Note: Always remember that the mass number is the total number of neutrons and protons in an atomic nucleus so sometimes more than and sometimes equal to its atomic number, depends upon no of neutrons in the element.