What is the difference between atomic and molecular mass?

Atomic mass refers to the mass of a single atom, while molecular mass refers to the total mass of a molecule.

Atomic mass, also known as atomic weight, is the weighted average mass of an atom of an element based on the relative abundance of different isotopes. It is usually expressed in atomic mass units (amu), where 1 amu is approximately equal to the mass of a single proton or neutron. The atomic mass of an element can be found on the periodic table and it gives us an idea of how much a single atom of that element weighs.

On the other hand, molecular mass (or molecular weight) is the sum of the atomic masses of all the atoms in a molecule. It is calculated by adding up the atomic masses of each constituent atom in the molecule. For example, the molecular mass of water (H2O) is calculated by adding the atomic masses of two hydrogen atoms and one oxygen atom.

It's important to note that while atomic mass is a property of a single atom, molecular mass is a property of a molecule, which can consist of multiple atoms of the same or different elements. Therefore, the molecular mass will always be equal to or greater than the atomic mass of its constituent elements.

Understanding the difference between atomic and molecular mass is crucial in chemistry, especially when dealing with reactions and stoichiometry. It allows us to calculate how much of a certain substance will react with or produce another substance, and it helps us understand the physical and chemical properties of different substances.