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.