Study guide: Chemical Composition of the Cell

📋 Course Outline

1. Atoms and Molecules
2. Elements and Chemical Compounds

📖 1. Atoms and Molecules

🔑 Key Concepts & Definitions

• Atom: The chemically indivisible smallest particle of a substance.
• Molecule: A group of atoms joined by chemical bonds.

★ Must-know

• Molecules of a given substance always contain the same kinds and numbers of atoms.

Further detail

• The diagram labels:

  • electrons
  • a nucleus
  • protons
  • neutrons

• An oxygen molecule contains two bonded oxygen atoms.

📖 2. Elements and Chemical Compounds

🔑 Key Concepts & Definitions

• Element: A substance consisting of only one kind of atom.
• Chemical compound: A substance made from atoms of different elements.

★ Must-know

• Scientists have identified 92 different kinds of atoms in nature, corresponding to 92 naturally occurring elements.

Further detail

• Different elements have distinct chemical and physical properties because they consist of their respective kinds of atoms; silver consists of silver atoms and gold of gold atoms.

• Table salt consists of sodium and chlorine; sugar consists of carbon, hydrogen, and oxygen; chalk consists of calcium, carbon, and oxygen.

💡 Memory Hook

An element contains one kind of atom; a compound combines different elements.

📊 Synthesis Tables

Elements and Compounds

Category	Atom composition	Example
Element	One kind of atom	Silver or gold
Chemical compound	Atoms of different elements	Salt, sugar, or chalk