AP Chemistry Unit 1 Review Flashcards

Topic 1.1 - Molar Mass

• Calculate quantities using dimensional analysis and the mole concept.
• Avogadro’s number (n = 6.022 × 10^{23} \text{ mol}^{-1}) connects moles to the number of particles.
• Molar mass (M) is numerically equal to the average mass in amu of one particle.
• Formula: n = \frac{m}{M}, where:
  • n = number of moles
  • m = mass of the sample
  • M = molar mass

Topic 1.2 - Mass Spectroscopy of Elements

• Mass spectra determine the identity and relative abundance of isotopes.
• Average atomic mass is estimated from the weighted average of isotopic masses.
• Mass Spectroscopy separates ionized atoms/molecules using magnetic fields or voltage.
  • Ionization
  • Acceleration
  • Deflection
  • Detection

Topic 1.3 - Elemental Composition of Pure Substances

• Pure substances contain either individual molecules or atoms/ions in fixed proportions (formula unit).
• Law of Definite Proportions: The ratio of constituent elements' masses in a pure compound is constant.
• Empirical formula: The simplest whole number ratio of atoms in a compound.

Topic 1.4 - Composition of Mixtures

• Mixtures contain two or more types of molecules/formula units with varying proportions.
• Elemental analysis determines the relative numbers of atoms and the purity of a substance.

Topic 1.5 - Atomic Structure and Electron Configurations

• Atoms consist of negatively charged electrons and a positively charged nucleus (protons and neutrons).
• Coulomb’s law calculates the force between charged particles.
• Electrons reside in shells (energy levels) and subshells (sublevels), described by electron configurations.
• Aufbau principle explains electron configuration.
• Ionization energy relates to the distance from the nucleus and the effective nuclear charge.
• Coulomb's Law: Like charges repel, opposite charges attract.
• Z_{eff} = Z – S where Z is the atomic number and S is the number of shielding electrons.

Topic 1.6 - Photoelectron Spectroscopy (PES)

• PES measures the energies of electrons in shells.
• Peak position in PES relates to the energy required to remove an electron.
• Peak height is proportional to the number of electrons in the subshell.
• Photoelectric Effect: emission of electrons from a surface in response to light.
  • Greater binding energy = electrons are closer to the nucleus.

Topic 1.7 - Periodic Trends

• Periodic table organization reflects recurring properties and electron configurations.
• Trends are understood via Coulomb’s law, shell model, and shielding/effective nuclear charge.
  • Ionization energy
  • Atomic and ionic radii
  • Electron affinity
  • Electronegativity
• Atomic radius:
  • Decreases: left to right.
  • Increases: down a group.
• Ionization energy:
  • Increases: left to right.
  • Decreases: down a group.
• Electron affinity:
  • Decreases: down a group
  • Increases: left to right
• Electronegativity:
  • Increases: left to right.
  • Decreases: down a group.
• Electronegativity: Ability to attract electrons.
• Electron affinity: Energy released when an electron is added.

Topic 1.8 - Valence Electrons and Ionic Compounds

• Chemical bond formation depends on valence electron interactions.
• Elements in the same group form analogous compounds.
• Ionic compound charges relate to periodic table position and valence electrons.