26. Which subatomic particle does not contribute significantly to an atom's mass?
Answer: C
The electron does not contribute significantly to an atom's mass.
Electrons have a negligible mass compared to protons and neutrons, making their contribution to the overall mass of an atom minimal.
A) Proton
Protons are one of the primary components of an atom's nucleus and have a significant mass. Each proton contributes approximately 1 atomic mass unit (amu), which is substantial compared to the mass of electrons.
B) Neutron
Neutrons also reside in the nucleus and carry a mass similar to that of protons, contributing to the overall mass of the atom. Like protons, each neutron adds approximately 1 amu to the atom's mass.
C) Electron
Electrons are much lighter than protons and neutrons, with a mass of about 1/1836 of a proton. Therefore, their contribution to the mass of an atom is minimal, making them the correct answer to the question.
D) All contribute to the atom's mass.
This statement is incorrect because, while protons and neutrons contribute significantly to the mass of an atom, electrons contribute very little. Thus, saying that all contribute equally is misleading.
Conclusion
The electron is the only subatomic particle listed that does not significantly impact an atom's mass, as its mass is negligible when compared to that of protons and neutrons. The other options fail to recognize the stark difference in mass contributions, confirming that the correct answer is indeed C.