Which of the following has the smallest total mass? A, two electrons B. two neutrons C. 1 electron plus 1 neutron D. 1 neutron plus 1 proton E. 2 protons
The Correct Answer and Explanation is:
ChatGPT said:
Correct Answer: A. Two electrons
Electrons possess the smallest mass among all stable subatomic particles found in atoms. The mass of a single electron is approximately 9.109 × 10⁻³¹ kilograms or 0.00054858 atomic mass units (amu). In contrast, protons and neutrons are much heavier. A neutron has a mass of approximately 1.008665 amu, and a proton has a mass of about 1.007276 amu.
To compare the total mass in each option:
- Option A (two electrons):
2 × 0.00054858 amu = 0.001097 amu - Option B (two neutrons):
2 × 1.008665 amu = 2.01733 amu - Option C (1 electron + 1 neutron):
0.00054858 + 1.008665 = 1.00921 amu - Option D (1 neutron + 1 proton):
1.008665 + 1.007276 = 2.01594 amu - Option E (two protons):
2 × 1.007276 = 2.01455 amu
From these calculations, option A clearly holds the lowest total mass. Even when paired with one neutron or proton, an electron’s extremely small mass contributes little to the total, but the moment heavier nucleons like protons or neutrons are included, the total mass increases significantly.
This highlights a fundamental characteristic of subatomic structure: electrons, while vital for chemical bonding and electric interactions, contribute negligibly to atomic mass. Most of an atom’s mass is concentrated in its nucleus, composed of protons and neutrons. Electrons orbit this dense center but barely affect the atom’s total mass.
Thus, among all the listed combinations, two electrons represent the smallest total mass.
