EXAM REVIEW

Radioactivity and Nuclear Decay

  • Radioactivity: Process where an unstable nucleus emits particles and energy. Radioisotopes are atoms with unstable nuclei that can change into different elements during decay.

  • Nuclear Radiation:

    • Alpha (\alpha): Positively charged (2 protons, 2 neutrons); least penetrating (stopped by paper).

    • Beta (\beta): Electrons emitted by a nucleus; more penetrating than alpha (stopped by aluminum).

    • Gamma (\gamma): High-energy rays with no mass or charge; most penetrating (reduced by lead or concrete).

  • Half-Life: Constant rate of decay; the time required for half a sample to decay.

    • # \text{ of half lives} = \frac{\text{total time of decay}}{\text{half-life}}

  • Fission & Fusion:

    • Fission: Splitting a nucleus into smaller parts.

    • Fusion: Combining nuclei to form a larger nucleus; occurs in stars at high temperatures.

Solutions and Solubility

  • Components: Solute (dissolved substance) and Solvent (dissolving medium).

  • Dissolving Processes: Dissociation (ionic), Dispersion (molecular), and Ionization (chemical change).

  • Physical Properties: Solutes increase conductivity, lower the freezing point, and raise the boiling point.

  • Solubility: Maximum solute in a solvent at a specific temperature.

    • Saturated: Max solute held.

    • Unsaturated: Less than max solute.

    • Supersaturated: More than normal max; unstable.

  • Concentration: Measured as Molarity (M).

    • \text{Molarity} = \frac{\text{moles of solute}}{\text{liters of solution}}

Acids, Bases, and Reactions

  • Acids: Produce hydronium ions (H_{3}O^{+}); sour, reactive with metals, pH < 7.

  • Bases: Produce hydroxide ions (OH^{-}); bitter, slippery, pH > 7.

  • Neutralization: Acid + Base \rightarrow Water + Salt.

  • Chemical Reactions: Reactants transform into products. Mass is conserved, requiring balanced equations using coefficients.

Atomic Theory History

  • Dalton: Elements are composed of atoms (solid spheres) that combine in fixed ratios.

  • Thomson: Discovered electrons using cathode rays; proposed the "plum pudding" model.

  • Rutherford: Discovered the dense, positive nucleus via the gold foil experiment; concluded atoms are mostly empty space.

  • Subatomic Particles:

    • Proton: Positive charge (+1), in nucleus.

    • Neutron: Neutral charge (0), in nucleus.

    • Electron: Negative charge (-1), outside nucleus.