BIO189 - CH. 2

LECTURE LEARNING OBJECTIVES

  • Define element, atom, subatomic particle, atomic number, mass number, atomic mass, isotope.

  • Identify valence and number of valence electrons in an atom.

  • Define intermolecular force and intramolecular force.

  • Define covalent bond, ionic bond, and hydrogen bond.

  • Differentiate between polar covalent and nonpolar covalent bonds.

  • Define ionic bond, cation, and anion.

  • Describe properties of water: universal solvent, adhesion, cohesion, high specific heat.

  • Explain hydrogen bonding characteristics of water.

  • Describe pH scale and relation of pH to H+ concentration.

  • Identify if a solution is acidic or basic based on pH.

ELEMENTS AND COMPOUNDS

  • Element: Cannot be broken down by chemical reactions.

  • Compound: Combination of two or more elements in a fixed ratio (e.g., NaCl).

  • Atom: Smallest unit of matter retaining properties of an element.

  • Subatomic particles: Protons (+), Neutrons (neutral), Electrons (-).

ATOMIC NUMBER AND MASS NUMBER

  • Atomic number: Number of protons (determines element).

  • Mass number: Protons + Neutrons.

  • Atomic mass: Average mass of all isotopes of an element.

  • Isotopes: Same protons, different neutrons (different mass).

ELEMENTS OF LIFE

  • Essential elements: Required for healthy life - CHONPS.

  • Trace elements: Required in minute quantities (<0.01%).

ELECTRON DISTRIBUTION

  • Reactivity depends on valence electrons in outer shell.

  • Valence: Electrons needed to complete outer shell.

CHEMICAL BONDS

  • Intramolecular forces: Hold atoms in a molecule.

  • Intermolecular forces: Exist between molecules.

  • Types of bonds:

    • Covalent bond: Sharing of valence electrons (single, double, triple bonds).

    • Ionic bond: Electron transfer, forms cation (+) and anion (-).

    • Hydrogen bonds: Noncovalent attractions involving hydrogen and electronegative atoms.

WATER

  • Water is a polar molecule, forms hydrogen bonds.

  • Cohesion: Hydrogen bonds between water molecules.

  • Adhesion: Water's attraction to other substances.

  • Specific heat: Energy required to change temperature (high specific heat due to hydrogen bonds).

  • Universal solvent: Dissolves ionic and polar substances (hydration shell forms around ions).

HYDROPHILIC AND HYDROPHOBIC SUBSTANCES

  • Hydrophilic: Has affinity for water (ionic or polar).

  • Hydrophobic: Repels water (nonionic, nonpolar).

SOLUTE CONCENTRATIONS

  • Concentration: Number of solute molecules in a volume.

  • Molarity: Moles of solute per liter of solution.

ACIDS AND BASES

  • Hydrogen ion transfer in water forms hydronium (H3O+) and hydroxide (OH-).

  • Concentrations of [H+] and [OH-] in pure water are equal.

pH SCALE

  • Measure of H+ concentration: pH = -log10([H+]).

  • Neutral pH: 7 (equal concentrations of H+ and OH-).

  • Low pH: Acidic ([H+] > [OH-]).

  • High pH: Basic ([H+] < [OH-]).