Question

question 13
where is most of the mass of an atom concentrated?
a nucleus
b neutrons
c protons
d orbitals
e electrons

Explanation:

An atom consists of a nucleus containing protons and neutrons, and electrons in orbitals. Protons and neutrons have much greater mass than electrons. The nucleus, which holds protons and neutrons, is where most of the atom's mass is concentrated.

Answer:

A. nucleus