Atoms

Atoms are the basic building blocks of matter. Everything around us, from the air we breathe to the food we eat, is made up of atoms. Understanding atoms is essential to understanding the world around us.

Structure of an Atom

Atoms are made up of three subatomic particles: protons, neutrons, and electrons. Protons and neutrons are located in the nucleus of the atom, while electrons orbit the nucleus in energy levels or shells.

Protons

Protons have a positive charge and are located in the nucleus of the atom. The number of protons in an atom determines its atomic number, which in turn determines the identity of the element.

Neutrons

Neutrons have no charge and are also located in the nucleus of the atom. They help stabilize the nucleus and contribute to the mass of the atom.

Electrons

Electrons have a negative charge and orbit the nucleus in energy levels. The outermost energy level, or valence shell, determines the atom's reactivity and ability to form chemical bonds.

Atomic Number and Mass Number

The atomic number of an atom is equal to the number of protons in its nucleus. The mass number is the sum of the number of protons and neutrons in the nucleus.

Isotopes

Isotopes are atoms of the same element that have different numbers of neutrons. This means they have the same atomic number but different mass numbers. Isotopes of an element have similar chemical properties but different physical properties due to their different masses.

Study Guide Questions

1. What are the three subatomic particles that make up an atom? Describe their properties and locations within the atom.
2. How do the atomic number and mass number of an atom relate to its composition?
3. Explain the concept of isotopes and how they differ from each other.
4. Why are electrons important in determining the chemical properties of an atom?

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