Chapter 2

Nature of Atoms (Page 1)

  • Matter

    • Has mass and occupies space.

    • Composed of atoms.

  • Importance of Atoms

    • Understanding atomic structure is essential for grasping biological molecules.

  • Rutherford Scattering Experiment

    • Conducted in the early 20th century.

    • Discovered the atom's physical nature and the existence of a central nucleus.

Atomic Structure (Page 2)

  • Components of Atoms

    • Protons

      • Positively charged particles located in the nucleus.

    • Neutrons

      • Neutral particles also found in the nucleus.

    • Electrons

      • Negatively charged particles located in orbitals surrounding the nucleus.

Atomic Number and Elements (Page 3)

  • Atomic Number

    • Equal to the number of protons, which equals the number of electrons in a neutral atom.

  • Definition of an Element

    • A substance that cannot be broken down by ordinary chemical means.

Atomic Mass (Page 4)

  • Mass vs. Weight

    • Mass is constant (same on Earth and Moon), while weight varies due to gravity.

  • Calculation of Atomic Mass

    • Atomic mass = Protons + Neutrons.

    • Mass of a proton and neutron is approximately 1 Dalton.

Electrons and Ions (Page 5)

  • Electrons

    • Located in orbitals surrounding the nucleus.

    • In a neutral atom, the number of electrons equals the number of protons.

  • Ions

    • Charged particles:

      • Cation: More protons than electrons (net positive charge).

      • Anion: Fewer protons than electrons (net negative charge).

Isotopes (Page 6)

  • Definition

    • Atoms of the same element with different numbers of neutrons.

  • Examples

    • Carbon has three isotopes: C12, C13, and C14.

  • Radioactive Isotopes

    • Unstable and emit radiation; decay at a constant rate.

    • Half-life examples: C14 (5,730 years), U238 (4.5 billion years).

Electrons and Chemical Behavior (Page 9)

  • Role of Electrons

    • Dictate the chemical nature of an atom.

    • The arrangement in the outermost orbital (valence orbital) is crucial for chemical behavior.

  • Energy Levels and Orbitals

    • Electrons occupy discrete energy levels (K, L, M, N) with sublevels called orbitals.

Chemical Bonds (Page 18)

  • Definition of Molecules and Compounds

    • Molecules: Groups of atoms held together.

    • Compounds: Molecules with more than one type of element.

  • Types of Chemical Bonds

    • Covalent Bonds: Sharing of electron pairs.

    • Ionic Bonds: Attraction between oppositely charged ions.

    • Hydrogen Bonds: Weak interactions involving hydrogen atoms.

Properties of Water (Page 33)

  • Cohesion and Adhesion

    • Cohesion: Water molecules stick to each other, creating surface tension.

    • Adhesion: Water molecules stick to other polar molecules, enabling capillary action.

  • Importance of Water

    • Stabilizes temperature, supports life, and facilitates chemical reactions.

Acids, Bases, and pH (Page 36)

  • Definitions

    • Acids: Proton donors.

    • Bases: Proton acceptors.

  • pH Scale

    • Most biological reactions occur between pH 6.5 and 8.0.

  • Buffers

    • Mixtures that resist changes in pH, composed of weak acids and their salts.

Biological Buffer Example (Page 41)

  • Carbonic Acid-Bicarbonate Buffer System

    • Involves carbon dioxide, carbonic acid, and bicarbonate ions to maintain pH balance in