Question

which statement is true? a the relative mass of an electron is negligible b atomic mass and average atomic mass are identical c all atoms have one or more neutrons d the number of protons and the number of neutrons in an atom are always the same

Explanation:

• Option A: The mass of an electron is about 1/1836 of the mass of a proton, so its relative mass is negligible. This is correct.
• Option B: Atomic mass is the mass of a single atom, while average atomic mass is the weighted - average of the masses of its isotopes. They are not identical.
• Option C: Hydrogen - 1 (protium) has 1 proton and 0 neutrons. So not all atoms have one or more neutrons.
• Option D: In an atom, the number of protons and neutrons is not always the same. For example, in carbon - 14, there are 6 protons and 8 neutrons.

Answer:

A. The relative mass of an electron is negligible