Atoms

Atoms are the basic building blocks of matter. They are the smallest unit of an element that retains the properties of that element.

Structure of an Atom

Atoms are composed of three main subatomic particles:

• Protons: Positively charged particles found in the nucleus of the atom.
• Neutrons: Neutral particles found in the nucleus of the atom.
• Electrons: Negatively charged particles found in orbitals around the nucleus.

Atomic Number and Mass Number

The atomic number of an atom is determined by the number of protons it contains. The mass number is the sum of the number of protons and neutrons in the nucleus.

Electron Orbitals

Electrons occupy specific energy levels or orbitals around the nucleus. These orbitals are designated by the letters s, p, d, and f.

Isotopes

Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. This results in variations in mass number.

Study Guide

1. What are the three main subatomic particles of an atom?
2. Explain the differences between atomic number and mass number.
3. Describe the arrangement of electrons in an atom.
4. What are isotopes and how do they differ from each other?

[Atoms] Related Worksheets and Study Guides:

• Atoms and Chemical BondingChemistry • High School
• Properties of atomsScience • Eighth Grade