Select the correct answer from each drop-down menu.

Much of the mass of an atom is concentrated in its nucleus. The nucleus contains

a - neutrons and electrons

b - protons and electrons

c - protons and neutrons

and the outer part of the atom contains

a - electrons

b - neutrons

c - protons

1) The answer is: c) protons and neutrons.

2) The answer is: a) electrons.

Neutron (n°) is a subatomic particle with no net electric charge.

Protons and neutrons are found in nucleus of an atom (atomic nuclei).

They are called nucleons and have masses of approximately one atomic mass unit.

Mass number (A) is sum of protons and neutrons in nucleus of an atom.

Protons and neutrons are hadrons composed of three valence quarks.

The electron (symbol: e⁻) is a subatomic particle whose electric charge is negative one elementary charge.

The electron has a mass that is approximately 1/1836 that of the proton (subatomic particle with a positive electric charge of + 1e elementary charge).

Protons and neutrons