Isotopes of an element differ in the number of neutrons in their atomic nuclei. While they have the same number of protons (which defines the element) and electrons (which largely determine chemical behavior), the difference in neutron number means isotopes have different atomic masses. This difference also leads to variations in physical properties such as stability, density, and radioactive behavior. Chemically, isotopes generally behave similarly, but heavier isotopes may react slightly more slowly due to their larger mass.

Key Differences Between Isotopes

• Neutrons : Different numbers of neutrons.
• Atomic Mass : Different mass numbers due to neutron count variation.
• Physical Properties : Can vary notably, including stability (some isotopes are radioactive), density, and melting points.
• Chemical Properties : Nearly identical, since the number of protons and electrons are the same, but slight kinetic isotope effects can occur.

Example

Hydrogen has three isotopes: protium (0 neutrons), deuterium (1 neutron), and tritium (2 neutrons). They behave similarly chemically but have different masses and radioactive properties in the case of tritium.

Thus, isotopes are atoms of the same element occupying the same position in the periodic table but differing in neutron number and atomic mass. This difference gives rise to varied physical properties while maintaining almost identical chemical characteristics.