Question

Why is most of the mass of an atom in the nucleus

Answer 1

This is because protons and neutrons are heavier than electrons as opposed to where electrons occupy most of an atoms volume

Answer 2

The nucleus contains the majority of an atom's mass because protons and neutrons are much heavier than electrons, whereas electrons occupy almost all of an atom's volume. The diameter of an atom is on the order of 10−10 m, whereas the diameter of the nucleus is roughly 10−15 m—about 100,000 times smaller.

Step-by-step explanation:

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