ML

APChem

Chapter 1

Periodic Table Basics

  • atomic number = number of protons
  • molar mass (grams) of element
  • horizontal = periods
  • vertical = groups
    • Group I = alkali metals
    • Group II = Alkaline Earth Metals
    • Group III - XII = Transition Metals
    • Group VII = Halogens
    • Group VIII = Noble Gases
  • mass number = sum of neutrons and protons
  • isotopes = elements (obviously same # of protons) varying neutrons

Moles

  • Avogadro’s # 6.022 * 10^23 particles per mole
  • M = molarity or mol/L (* remember mol is moles)
  • moles = grams/molar mass
  • moles = PV/RT
    • P = pressure (atm)
    • volume (L)
    • temperature K)
    • R = gas constant 0.0821 (L atm / mol K)
    • many gas occur at STP (standard temperature pressure), P = 1 atm and T = 273 K
    • can convert directly between volume of gas and number of moles
  • moles = liters/ (22.4 L/mol)

Molarity

  • M = moles of solute / liters of solution

Percent Composition

  • To calculate you must separate the compound by elements
  • Take the molar mass of each and find the mass of each element in compound
  • convert by dividing each mass of substance by the TOTAL mass of ENTIRE compound and multiply by 100

Empirical & Molecular Formulas

  • Finding empirical formula of compound
    • start by assuming the percentages total up to 100g (ex: 55.6% is 55.6 g or 7.11% is 7.11g)
    • Divide each gram you get by the molar mass of the pure element
    • Divide all the moles now by the lowest number of moles calculated above
    • Should receive the subscript of the elements in formula
  • Find the molecular formula from empirical formula
    • Find mass each element
    • Use molar mass of element x subscript
    • Combine to find total molar mass of compound
    • divide mass given by molar mass of compound and find molecular formula

Coulomb’s Law concepts

  • F(columbic) = magnitude of positive charge x magnitude of negative charge / distance btwn negative charge

Bohr’s Model

  • electromagnetic radiation: electrons jump to higher energy level

Photoelectron spectroscopy

  • ionization energy: amt of energy necessary for electrons to be ejected
  • kinetic energy: energy of incoming radiation must be conserved & any of energy that does not go into breaking electron free from nucleus is converted in KE
    • EQUATION: incoming radiation energy = binding energy + kinetic energy (ejected electrons)

Spectra

  • photoelectron spectrum (PES): amt of ionization energy for all electrons ejected from nucleus
  • subshells: shape of space electron can be found

Electron Configuration

  • s subshell: max 2
  • p subshell: max 6
  • d subshell: max 10
  • f subshell: max 14
  • Shorthand or normal notation (remember brackets for shorthand)

Aufbau principle: building up electron config of atom, electrons placed in orbitals, subshells, and shells in order of increasing energy

Pauli Exclusion Principle: two electrons share orbital cannot have same spin * when draw arrows make sure they are opposite

Hund’s Rule: when electron is added to subshell, always occupy empty orbital if one is available

Predicting Ionic Change:

  • valence electrons in outermost s and p subshells
  • ion: atom either gained or lost electrons
  • cation (positive charge) anion (negative charge)

Periodic Trends

  1. electrons are attracted to protons in nucleus of atom
  • closer electron is to nucleus, more strongly it is attracted
  • more protons in nucleus, more strongly electron is attracted
  1. electrons repelled by other electrons in atom; electrons are between valence and nucleus, valence electron will be less attracted to nucleus (electron shielding)
  2. completed shells are “stable”; atoms will add or subtract valence electrons to create 'complete’ shells if possible

Atomic Radius

  • approximate distance form nucleus of atom to its valence electrons
  • LEFT TO RIGHT OF PERODIC TABLE
    • protons are added to nucleus → valence electrons more strongly attracted → decreases atom radius
    • IF electrons added in same shell, NOT much shielding effect since abt same distance from nucleus
  • TOP TO BOTTOM OF PERODIC TABLE
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