What is the approximate mass of an electron?

The approximate mass of an electron is indeed very small, often referred to as being "almost 0" in comparison to the mass of protons and neutrons, which make up the nucleus of an atom. The actual mass of an electron is about 9.11 x 10^-31 kilograms, which is significantly less than that of a proton (approximately 1.67 x 10^-27 kg).

This tiny mass is crucial in various aspects of chemistry and physics, particularly in atomic theory and quantum mechanics. Electrons are involved in chemical bonding and reactions, and their mass (being so small) means that they have a relatively insignificant impact on the overall mass of an atom compared to the nucleus. Thus, referring to the mass of an electron as "almost 0" effectively captures the practical relevance of its mass when considering atomic and molecular weight calculations.

Understanding the remarkably small mass of electrons helps illustrate why, in many scenarios, their contribution to the overall mass of an atom can be overlooked in simplified calculations.