What does the atomic mass of an element include? Electrons only Neutrons plus electrons Protons plus neutrons Protons plus electrons plus neutrons Neutrons only Protons only Protons plus electrons Previous

The **atomic mass** of an element primarily includes the combined masses of its **protons and neutrons** in the nucleus. While electrons do contribute to the overall charge of the atom, their mass is relatively negligible compared to protons and neutrons. **Correct Answer:** - **Protons plus neutrons** **Explanation:** - **Protons and Neutrons:** These are the particles that reside in the nucleus of an atom and contribute most significantly to its mass. Each proton and neutron has a mass of approximately 1 atomic mass unit (amu). - **Electrons:** Although electrons are part of an atom, their mass is about 1/1836 that of a proton, making their contribution to atomic mass virtually insignificant for most practical purposes. **Incorrect Options:** - **Electrons only:** Electrons contribute negligibly to atomic mass. - **Neutrons plus electrons:** While neutrons contribute to mass, electrons do not significantly. - **Protons plus electrons plus neutrons:** Including electrons is unnecessary as their mass is minimal. - **Neutrons only:** Protons also contribute significantly. - **Protons only:** Neutrons also contribute significantly. - **Protons plus electrons:** Neutrons are missing, which are essential for atomic mass. Understanding that atomic mass is primarily determined by protons and neutrons helps in comprehending various aspects of chemistry and physics, including isotopic variations and the behavior of elements in different reactions.