Question

An isotope of an element, atomic number Z, has a mass number 2z+4. How many neutrons are there in the nucleus of the element?

*MULTIPLE CHOICE*
A) Z+4
B) Z+2
C) Z
D) 4

Answer 1

A) Z + 4

In the actual atom, half of the nucleus would be protons and the other half neutrons, hence the 2z. The additional four in the expression must be neutrons because adding protons would change the element all together.

Answer 2

A) Z+4

Step-by-step explanation:

Atomic number of the isotope = Z

Mass number of the isotope = 2Z+4.

Atomic number = Number of protons in the atom = Number of electrons in the atom

Mass number = Number of protons in the atom + Number of neutrons in the atom

Hence number of neutrons = Mass number - Number of protons

= 2Z + 4 - Z = Z + 4

Hence the required answer to the question is represented by option A which is Z + 4.