Question

A student wants to draw a model of an atom. Which statement describes how to find the number of neutrons to include in the model?

A. Add the atomic number and the mass number.
B. Add the number of electrons to the number of protons.
C. Subtract the number of electrons from the number of protons.
D. Subtract the atomic number from the mass number. ​


Anything helps.

Answer 1

The number of electrons is not important (eliminate B and C)

The mass number is equal to or greater than the atomic number

(this leaves only D)

Mass number is the total mass of the nucleus (neutrons + protons)

Subtracting the atomic number from the mass number gives:

Mass number - Atomic number = number of neutrons