Jeffrey is making a model of tungsten for his chemistry class. He has foam balls for the protons, neutrons, and electrons. He has added 21 electrons to his model so far. How many more electrons does he need to add to complete his neutral atom of tungsten?

A. 1

B. 22

C. 31

D. 53

Atomic number (Z) of tungsten is 74

Mass number (A) of tungsten is 184

Now:

Atomic number of an element = Number of protons = Number of electrons

Mass number = Number of Protons + Number of neutrons

In the case of tungsten

Total Number of electrons = 74

Jeffrey has already added 21 electrons

Number of electrons needed = 74 - 21 = 53

Ans (D) 53 more electrons are needed to complete the neutral atom of tungsten.