Structure of the Atom and Isotopes

Subatomic Particles

Protons, Neutrons, Electrons
- Relative Mass:
  - Proton: 1 amu
  - Neutron: 1 amu
  - Electron: "0" amu (actual mass is 1/1000 of a proton's mass)
- Relative Charge:
  - Proton: +1
  - Neutron: neutral
  - Electron: -1
- Location:
  - Proton and Neutron: nucleus
  - Electron: outside the nucleus

Classic Model: Misleading proportions (nucleus too large)
Accurate Visual:
- Analogy: Atom = sports stadium, Nucleus = a single pea in the stadium
- Proportions:
  - Nucleus: Tiny, highly dense, positive charge
  - Outside Nucleus: Large volume, low density, negative charge (electrons)
- Density Analogy: Nucleus density compared to ordinary matter (e.g., gold ring x 1,000,000)

Format: Elemental Symbol
- Upper left: Mass number (protons + neutrons)
- Lower left: Atomic number (number of protons)
- Upper right: Charge (protons - electrons)
Example:
- Isotope Notation: ^31_15 Element^3-
  - Protons: Equal to atomic number (15)
  - Mass Number: 31 (protons + neutrons)
  - Charge: -3 (protons - electrons)
  - Neutrons: Mass number - protons = 16
  - Electrons: Charge = protons - electrons; solve algebraically (15 - (-3) = 18)

Definition: Same element, different mass (different number of neutrons)
- Examples of Carbon Isotopes:
  - Carbon-12, Carbon-13, Carbon-14
  - Common in periodic table format
  - Weighted average mass (e.g., Carbon: 12.011)

Mass Number: Weighted average of all isotopes
- Cannot derive isotopes from average mass

Average Mass: 79.90 (close to 80, but no actual isotope of 80)
- Main Isotopes: Bromine-79 (50.7%), Bromine-81 (49.3%)
Grades Analogy:
- Course Average: Doesn't represent individual test scores; like isotope mass average
- Directionality: Specific information (isotopes + abundance) to calculate average, but not vice versa