# 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

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