Question

A certain radionuclide is used to diagnose lymphoma. An atom of this radionuclide contains 31 protons and 36 neutrons. Which statement is correct about the radionuclide?
A.The atomic number is 31, the mass number is 67, and its symbol is 67/31 GA.
B.The atomic number is 31, the mass number is 67, and its symbol is 31/64 GA.
C.The atomic number is 67, the mass number is 31, and its symbol is 67/31 GA .
D.The atomic number is 67, the mass number is 31, and its symbol is 31/64 GA .

Answer 1

The atomic number is the total number of protons in the nucleus. The mass number is the total number of particles in the nucleus. That includes the neutrons and the protons. So, the atomic number is 31. When you look at the element on the periodic table with a designated atomic number of 31, that would be Gallium, with a symbol of Ga. Mass number is 31 + 36 = 67. So, the answer is A.

Answer 2

Answer:  A. The atomic number is 31, the mass number is 67, and its symbol is $_{31}^{67\textrm{Ga}$

Explanation:

Atomic number is defined as the number of protons or number of electrons that are present in an electrically neutral atom.

Atomic number = Number of protons = 31

Mass number is defined as the sum of number of protons and neutrons that are present in an atom.

Mass number = Number of protons + Number of neutrons  = 31 + 36 = 67

The isotopic representation of a radionuclide is: $_Z^A\textrm{X}$

where,

Z = Atomic number of the atom

A = Mass number of the atom

X = Symbol of the atom

Thus the atom is written as $_{31}^{67\textrm{Ga}$