Isotopes of an element differ in their:A. atomic numberB. number of neutronsC. position in the Periodic TableD. electronic arrangement

Isotopes of an element differ in their number of neutrons. So, the correct answer is B. number of neutrons.

Here's why:

Isotopes are variants of a particular chemical element which differ in neutron number, and consequently in nucleon number. All isotopes of a given element have the same number of protons but different numbers of neutrons in each atom.

A. Atomic number: This is not correct because isotopes of an element have the same atomic number, which is the number of protons in the nucleus of an atom.

C. Position in the Periodic Table: This is not correct because isotopes of an element do not change the element's position in the Periodic Table. The position is determined by the atomic number.

D. Electronic arrangement: This is not correct because isotopes of an element have the same electronic arrangement. The electronic arrangement is determined by the number of electrons, which equals the number of protons in a neutral atom.