Differences Between Atom, Element, Molecule, and Compound

Introduction

• Atoms are the smallest units of matter.
• Everything in the universe is made up of atoms (e.g. plants, animals, food, water).

Why Are Things Different?

• There are 118 different types of atoms (elements) present in the universe.
• Different combinations of atoms produce different substances.

Key Terms

• Atom: The smallest unit of matter.
• Element: A substance made up of a single type of atom.
• Molecule: A group of atoms bonded together.
• Compound: A substance formed from two or more different types of atoms bonded together.

Types of Atomic Combinations

Homo-Atomic Combination

• Definition: Combinations of the same type of atoms.
• Molecule Formation:
  • When an atom/group of atoms exist freely, it forms a molecule.
• Types of Homoatomic Molecules:
  • Monoatomic Molecules:
    • Examples: Neon, Argon, Xenon (Noble gases, made of one atom).
  • Diatomic Molecules:
    • Examples: H2 (hydrogen), O2 (oxygen), N2 (nitrogen).

Element Formation

• Many monoatomic or diatomic molecules combine to form elements.
• Example:
  • Many Neon atoms = Neon Element.
  • Many H2 molecules = Hydrogen Element.

Hetero-Atomic Combination

• Definition: Combinations of different types of atoms.
• Formation of Heteroatomic Molecules:
  • Examples: CO2 (carbon dioxide), H2O (water), CH4 (methane).
• Compound Formation:
  • When many heteroatomic molecules combine, they form a compound.

Summary of Examples

• Hydrogen (H): An atom.
• H2: A homoatomic molecule or elemental molecule.
• H2O: A heteroatomic molecule.
• Glass of Water: A compound.

Conclusion

• Understanding the distinctions between atoms, elements, molecules, and compounds is essential for studying chemistry.