Structure of the Atom

Chapter 2: Johnston - Structure of the Atom

1. Definition of Atom

• An atom is the basic building block of matter.

2. What is the nucleus made of?

• The nucleus of an atom is made up of protons and neutrons.
• Collectively termed as nucleons, these particles reside in the nucleus at the center of the atom.

3. What is a nucleon?

• A nucleon is a particle that exists in the atomic nucleus.
• Nucleons include both protons (positively charged) and neutrons (no electrical charge).

4. Explain the mass of the nucleus

• The mass of the atomic nucleus is less than the sum of the masses of the individual nucleons that constitute the nucleus.
• This mass difference occurs due to the binding energy that holds the nucleus together, which cannot be accounted for by simply summing individual nucleon masses.

5. Describe electrons

• Electrons are negatively charged particles that orbit the nucleus of an atom.
• They exist in defined energy levels and distances from the nucleus, determining the atom's electron configuration.

6. Describe protons

• Protons are positively charged particles located in the nucleus.
• Each proton has a mass of approximately $1.673 imes 10^{-27} ext{ kg}$.

7. Describe neutrons

• Neutrons are neutral particles found in the nucleus; they carry no electrical charge.
• The mass of a neutron is about $1.675 imes 10^{-27} ext{ kg}$.

8. Explain the concept of how atoms get their charge

• Atoms obtain their charge due to the loss or gain of electrons.
• When an atom loses electrons, it becomes positively charged (cation), while gaining an extra electron results in a negative charge (anion).

9. What is an anion?

• An anion is a negatively charged ion formed when an atom gains one or more electrons.
• This gain of electrons leads to an excess of negative charge compared to the number of protons in the nucleus.