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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