Which of the following statements regarding isotopes is TRUE?

a. Isotopes have the same number of protons and neutrons, but vary in the number of electrons they contain.
b. Isotopes of an element have the same atomic number, but have different atomic masses.
c. The chemical properties of ALL of an element's isotopes are EXACTLY the same.
d. The atomic weight of any element is approximately equal to the mass number of its most abundant isotope.
e. B, C, and D. All of the statements are true regarding isotopes

e

Explanation:

A. Is wrong

Isotopes do not have same number of neutrons. They only contain the same number of protons and hence same number of electrons.

B is correct

Isotopes are the different atoms of a particular single element which have exactly the same number of protons but varying number of neutrons.

C is correct

The chemical properties are a function of the electrons since they are the ones involved in chemical bonding. Since the number of electrons are the same, it is expected that they have similar chemical properties.

d is correct

It is the weight of the most abundant isotope that clearly determines the weight of the atom. In fact, the weight of the atom is closest in value to the weight of the atom with the highest abundance

e is correct as all the options here are correct

D is wrong, not all options are correct