Question

Answer the following questions without referring to Table 2.1: (a) What are the main subatomic particles that make up the atom? (b) What is the relative charge (in multiples of the electronic charge) of each of the particles? (c) Which of the particles is the most massive? (d) Which is the least massive?

Short answer

(a) Protons, neutrons, electrons. (b) +1, 0, -1. (c) Neutron. (d) Electron.

Step-by-step solution

Identify Main Particles

Atoms are composed of three main subatomic particles: protons, neutrons, and electrons.

Determine Particle Charges

Protons have a positive charge of +1, electrons have a negative charge of -1, and neutrons have no charge (0). These charges are in multiples of the elementary charge, which is the charge of one electron in magnitude.

Compare Particle Masses

Protons and neutrons are similar in mass, but neutrons are slightly more massive. Electrons are much less massive than both protons and neutrons.

Identify Most and Least Massive Particles

The neutron is the most massive particle in the atom, while the electron is the least massive.

Key concepts

Atomic Structure

Atoms form the foundation of all matter in the universe. They are remarkably tiny and largely self-contained. Inside each atom, you'll find three primary subatomic particles:

• Protons are located in the nucleus, the tiny dense center of the atom. They carry a positive charge and are key to the atom's identity since they determine the atomic number, which tells us what element the atom belongs to.


• Neutrons are also housed in the nucleus and are similar to protons in size and mass, but they do not carry a charge, which is why they are sometimes considered neutral particles.


• Electrons spin around the nucleus in regions called electron clouds. Contrary to protons and neutrons, electrons are much smaller and carry a negative charge.

The arrangement of these subatomic particles defines the unique structure of each atom. The balance between the positive protons and negative electrons controls the overall charge and stability, contributing to the vast array of chemical elements and compounds we see.

Particle Charge

Each subatomic particle can be distinguished by its charge, which affects how it interacts with other particles.

• Protons have a positive charge, designated as +1. This charge is considered in terms of the elementary charge: the charge of an electron but positive.


• Neutrons, in fact, do not carry any charge, making them neutral. This neutrality helps stabilize the nucleus, preventing protons from repelling each other.


• Electrons carry a negative charge of -1. Their movement around the nucleus is essential in the formation of ions and molecules as they can be transferred or shared in chemical reactions.

Traditional chemical reactions typically involve the exchange or sharing of electrons, due to their charge, whereas protons and neutrons remain in the nucleus, maintaining the atom's structure.

Particle Mass

When discussing subatomic particles, it's important to note their respective masses, as they dictate the atom's weight.

• Protons have a relative mass of 1 atomic mass unit (amu), similar to neutrons. They significantly contribute to the total mass of an atom.


• Neutrons, although slightly more massive than protons, also approximate to 1 amu. Their similar mass to protons ensures the nucleus is dense and stable.


• Electrons are the lightweights of the atomic world, with a mass of about 1/1836th that of a proton or neutron. This means that even though electrons are vital for chemical interactions, they do not significantly affect the atom’s mass.

These particle masses influence how atoms and molecules behave, from the smallest cells in biology to the largest phenomena in astrophysics.