AP Chemistry Exam Review 2026 |
Comprehensive Study Guide, Practice
Questions, Answers & FRQ Prep |
Complete Ethics Study
Guide
Updated 2026 Questions and Answers
100% Verified Exam Prep and Comprehensive
Rationales
Included
,atomic number The same as the number of protons in the nucleus of an element; it is also
the same as the number of electrons surrounding the nucleus of an element
when it is neutrally charged.
mass number The sum of an atom's neutrons and protons
isotopes Atoms of an element with different numbers of neutrons
Avogadro's number 6.022×10²³ particles per one mole
Moles grams/molar mass
Standard Temperature and Pressure (STP) Pressure = 1 atm
Temperature = 273 K
Converting from moles to liters I mole of gas = 22.4 L
Moles and Solutions Moles = (molarity)(liters of solution)
percent composition (mass percents) The percent by mass of each element that makes up a compound. It is
calculated by dividing the mass of each element or component in a
compound by the total molar mass for the substance.
empirical formula - Represents the simplest ratio of one element to another in a compound
- Start by assuming a 100 g sample
- Convert percentages to grams
- Convert grams into moles
- Divide each mole value by the lowest of the values
- These values become the subscripts
molecular formula - Determine the molar mass of the empirical formula
- Divide that mass into the molar mass
x = m/e
x = molar mass/ empirical mass
- Multiply all subscripts in the empirical formula by the value of x
Aufbau principle States that when building up the electron configuration of an atom,
electrons are placed in orbitals, subshells, and shells in order of increasing
energy.
, Pauli Exclusion Principle States that the two electrons which share an orbital cannot have the same
spin. One electron must spin clockwise, and the other must spin
counterclockwise.
Hund's Rule States that when an electron is added to a subshell, it will always occupy an
empty orbital if no one is available. Electrons always occupy orbitals singly
if possible and pair up only if no empty orbitals are available.
Coulomb's Law The amount of energy that an electron has depends on its distance from
nucleus of an atom. While on the exam, you will not be required to
mathematically calculate the amount of energy a given electron has, you
should be able to qualitatively apply Coulomb's Law.
Essentially, the greater the charge of the nucleus, the more energy an
electron will have.
Quantum Theory Max Planck figured out that electromagnetic energy is quantized. That is,
for a given frequency of radiation (or light), all possible energies are
multiples of a certain unit of energy, called a quantum (mathematically,
that's E = hv). So, energy changes do not occur smoothly but rather in small
but specific steps.
Energy and Electromagnetic Radiation ΔE = hv = hc/λ
ΔE = energy change
h = Planck's constant, 6.626×10⁻³⁴ J∙s
v = frequency of the radiation
λ = wavelength of the radiation
c = the speed of light, 3.00×10⁸ m/s
Frequency and Wavelength c = λv
*Inversely proportional*
c = speed of light in a vacuum (2.998×10⁸ m/s)
λ = wavelength of the radiation
v = frequency of the radiation
ionization energy The amount of energy necessary to remove an electron from an atom.
photoelectron spectra (PES) A chart of the amount of ionization energy for all electrons ejected from a
nucleus.
The y-axis describes the relative number of electrons that are ejected from
a given energy level.
The x-axis shows the binding energy of those electrons.
Gases will most likely act as ideal under what conditions? High temperature and low pressure
Comprehensive Study Guide, Practice
Questions, Answers & FRQ Prep |
Complete Ethics Study
Guide
Updated 2026 Questions and Answers
100% Verified Exam Prep and Comprehensive
Rationales
Included
,atomic number The same as the number of protons in the nucleus of an element; it is also
the same as the number of electrons surrounding the nucleus of an element
when it is neutrally charged.
mass number The sum of an atom's neutrons and protons
isotopes Atoms of an element with different numbers of neutrons
Avogadro's number 6.022×10²³ particles per one mole
Moles grams/molar mass
Standard Temperature and Pressure (STP) Pressure = 1 atm
Temperature = 273 K
Converting from moles to liters I mole of gas = 22.4 L
Moles and Solutions Moles = (molarity)(liters of solution)
percent composition (mass percents) The percent by mass of each element that makes up a compound. It is
calculated by dividing the mass of each element or component in a
compound by the total molar mass for the substance.
empirical formula - Represents the simplest ratio of one element to another in a compound
- Start by assuming a 100 g sample
- Convert percentages to grams
- Convert grams into moles
- Divide each mole value by the lowest of the values
- These values become the subscripts
molecular formula - Determine the molar mass of the empirical formula
- Divide that mass into the molar mass
x = m/e
x = molar mass/ empirical mass
- Multiply all subscripts in the empirical formula by the value of x
Aufbau principle States that when building up the electron configuration of an atom,
electrons are placed in orbitals, subshells, and shells in order of increasing
energy.
, Pauli Exclusion Principle States that the two electrons which share an orbital cannot have the same
spin. One electron must spin clockwise, and the other must spin
counterclockwise.
Hund's Rule States that when an electron is added to a subshell, it will always occupy an
empty orbital if no one is available. Electrons always occupy orbitals singly
if possible and pair up only if no empty orbitals are available.
Coulomb's Law The amount of energy that an electron has depends on its distance from
nucleus of an atom. While on the exam, you will not be required to
mathematically calculate the amount of energy a given electron has, you
should be able to qualitatively apply Coulomb's Law.
Essentially, the greater the charge of the nucleus, the more energy an
electron will have.
Quantum Theory Max Planck figured out that electromagnetic energy is quantized. That is,
for a given frequency of radiation (or light), all possible energies are
multiples of a certain unit of energy, called a quantum (mathematically,
that's E = hv). So, energy changes do not occur smoothly but rather in small
but specific steps.
Energy and Electromagnetic Radiation ΔE = hv = hc/λ
ΔE = energy change
h = Planck's constant, 6.626×10⁻³⁴ J∙s
v = frequency of the radiation
λ = wavelength of the radiation
c = the speed of light, 3.00×10⁸ m/s
Frequency and Wavelength c = λv
*Inversely proportional*
c = speed of light in a vacuum (2.998×10⁸ m/s)
λ = wavelength of the radiation
v = frequency of the radiation
ionization energy The amount of energy necessary to remove an electron from an atom.
photoelectron spectra (PES) A chart of the amount of ionization energy for all electrons ejected from a
nucleus.
The y-axis describes the relative number of electrons that are ejected from
a given energy level.
The x-axis shows the binding energy of those electrons.
Gases will most likely act as ideal under what conditions? High temperature and low pressure
