Question

Boron occurs naturally as two isotopes. What is the difference between these isotopes?

Answer 1

"They have different numbers of neutrons and different mass numbers.  Remember mass number is protons plus neutrons. The number of protons for an element will never change, however the number of neutrons can." I took the test, its D

Answer 2

Answer: The two isotopes of boron differs in mass number rather than atomic number.

Explanation:

Isotopes are defined as the chemical species that have same atomic number but differ in their mass number.

Boron is the 5th element of the periodic table and have 2 naturally occurring isotopes. The isotopes are : B-10 and B-11

For $_5^{10}\textrm{B}$ isotope:

Percentage abundance of this isotope = 20 %

Atomic number = 5

Mass number = 10

For $_5^{11}\textrm{B}$ isotope:

Percentage abundance of this isotope = 80 %

Atomic number = 5

Mass number = 11

Hence, the two isotopes of boron differs in mass number rather than atomic number.