Question

How are isotopes of the same chemical element alike? How are they different?

Answer 1

Answer: The atomic mass of these species is different and atomic number remains same.

Explanation:

Isotopes are the chemical species of the same element having different number of neutrons.

• Atomic number is equal to the number of protons or electrons present in that element.

Atomic Number = Number of electrons = Number of protons

• Atomic mass is defined as the sum of number of protons and neutrons contained in an atom.

Atomic Mass = Number of protons + Number of neutrons

For isotopes, as the number of neutrons differ, the atomic mass also differs.

For Example: Carbon has 3 naturally occurring isotopes: $_6^{12}\textrm{C},_6^{13}\textrm{C}\text{ and }_6^{14}\textrm{C}$. The atomic number remains the same but atomic mass differs.

Hence, for isotopes, the atomic mass of these species is different and atomic number remains same.