Ap Chemistry Princeton Review

• Relative abundance

  Percentage of each isotope
• Moles=

  1. Particles / (6.022 x 10^23)

  2. Grams / molar mass

  3. PV / RT
• Calculating percent composition

  1. Determine the number of each atom present in a compound

  2. Multiply the number of atoms by their atomic masses

  3. Add up the masses of the individual elements for the total mass of the compound

  4. Divide the individual masses by the total mass
• Empirical formula

  Represents the simplest ratio of one element to another in a compound
• Molecular formula

  Represents the actual formula for a substance
• Determining the molecular formula for a compound given its molar mass

  1. Determine the molar mass of the empirical formula

  2. Divide the given mass by the empirical molar mass

  3. Multiply all subscripts by that value
• To remove an electron from an atom, the electrostatic forces must be overcome by adding energy (binding energy)
• Ionization energy

  The amount of energy needed to eject an electron from its energy level, same as binding energy
• Photoelectron Spectroscopy

  Incoming Radiation energy = Ionization Energy + Kinetic Energy
• Electron configuration


  The complete description of the energy level & subshell that each electron on an element inhabits
• Valence electrons


  Electrons on the outermost s & p subshells
• Elements on the right side of the periodic table tend to form anions, elements on the left side tend to form cations, transition metals have ions of varying charges
• Periodic Trends


  • Electrons are attracted to the protons of the nucleus, closer the electron is to the nucleus = stronger attraction, more protons in the nucleus = stronger attraction
  • Electrons are repelled by other electrons in an atom, shielding effect
  • Completed shells (sometimes completed subshells) are very stable, and atoms will add or subtract valence electrons to complete shells if possible
  • Metals are on the left side and give up electrons, nonmetals are on the right and gain electrons
  • Metalloids are the elements between metals & nonmetals
• Electron affinity


  The energy change that occurs when an electron is added to an atom in its gaseous state
• Ionic bonds


  Held together by electrostatic attraction between ions in a lattice structure, occur between metals & nonmetals
• Ionic solids


  • Usually solid at room temperature and have high melting & boiling points
• Factors affecting the melting points of ionic substances


  • Charge ↑ Lattice energy ↑
  • Size ↓ Coulombic attraction ↑
• Metallic bonds


  Held together by a sea of electrons, the nucleus & core electrons are stationary while valence electrons can move
• Types of covalent bonds

  • Single bonds: One sigma (σ), Bond Order: One, Bond Length: Longest, Bond Energy: Least
  • Double bonds: One sigma (σ) & one pi (π), Bond Order: Two, Bond Length: Intermediate, Bond Energy: Intermediate
  • Triple Bonds: One sigma (σ) & two pi (π), Bond Order: Three, Bond Length: Shortest, Bond Energy: Greatest
• Network covalent bonds


  Atoms are led together in a lattice of covalent bonds, very solid and have high boiling & melting points, electrons are localized in covalent bonds & cannot move in the lattice, poor conductors of electricity
• Conductivity of different types of bonds

  • Ionic: Solid: No, Aqueous: Yes, Liquid: Yes, Gas: No
  • Molecular Covalent: Solid: No, Aqueous: No, Liquid: No, Gas: No
  • Network Covalent: Solid: No, Aqueous: n/a, Liquid: No, Gas: No
  • Metallic: Solid: Yes, Aqueous: n/a, Liquid: Yes, Gas: No
• Drawing Lewis Dot Structures

  1. Count the valence electrons in the molecule/polyatomic ion

  2. Add electrons for negative charges, subtract electrons for positive charge

  3. Draw the skeletal structure with the least electronegative atom in the middle

  4. Draw single bonds (2 electrons) between bonded atoms, subtracting as many electrons added from the total

  5. Add electrons to surrounding atoms until each has a complete valence shell

  6. Add remaining electrons to the central atom

  7. <8: Add more bonds between the central atom & an outer atom until it has a complete valence shell

  8. =8: Complete octet, no change

  9. Some atoms can have more than 8 but no more than 12
• Resonance forms


  The varying forms of a molecule with respect to the double/triple bond between its central atom & outer atoms
• Formal charge


  Determines the most likely structure of a molecule if it has multiple valid Lewis structures, calculated by subtracting the number of assigned electrons from the number of valence electrons for each atom
• Valence Shell Electron Pair Repulsion (VSEPR)


  • The model the 3-D geometries of molecules are based on, determined by the number of electron pairs (bonding & lone pairs) on the central atom
• Nonpolar covalent bond

  A covalent bond in which electrons are shared equally & no dipole is present
• A molecule's polarity depends on its bonds' polarity & molecular geometry
• Trigonal Planar

  sp2 hybridization, 3 bonded pairs, 120°
• Trigonal Pyramidal

  sp3 hybridization, 3 bonded pairs & 1 lone pair, <109.5°
• Bent

  sp3 hybridization, 2 bonded pairs & 2 lone pairs, <109.5°
• Trigonal Bipyramidal

  sp4 hybridization, 5 bonded pairs, 120° & 90°
• Seesaw

  sp4 hybridization, 4 bonded pairs & 1 lone pair, <120° & <90°
• T Shaped

  sp4 hybridization, 3 bonded pairs & 2 lone pair, <90°
• Linear

  sp4 hybridization, 2 bonded pairs & 3 lone pair, 180°
• Octahedral

  sp5 hybridization, 6 bonded pairs, 90°
• Square Pyramidal

  sp5 hybridization, 5 bonded pairs & 1 lone pair, <90°
• Square Planar

  sp5 hybridization, 4 bonded pairs & 2 lone pairs, 90°
• Polarity: Polar covalent - a covalent bond in which electrons are shared unequally
• Dipole

  A pair of opposite electric charges separated by some distance
• Nonpolar covalent - a covalent bond in which electrons are shared equally & no dipole is present