AP Chemistry Units 1-5 Study Guide [INCOMPLETE]

made this for my midterm cus were just doing 1-5, but its out for the public to use for whatever because ap chem is hard

Atomic Mass Unit

Unit for the mass of an atom, abbreviated to amu and based on C-12, which is 12 amu.

Molar Mass

The conversion factor between grams (g) and moles (mol), found by multiplying the number of atoms by the masses of each atom and adding for the total.

Avogadro’s Number

Used to find the number of atoms in a mole of a substance: conversion is 6.022 × 10²³

Atomic Number

Proton count in the element

Mass Number

The combined number of protons and neutrons in an element

Isotope

Specific formation of an element defined by how many neutrons there are

Average Atomic Mass Formula

∑(abundance of isotope n) × (mass of isotope n). Uses isotope’s weighted average.

Mass Spectra/Spectrometry

Measures percent abundances and masses of different isotopes. The diagrams are sorted by ratio of mass to charge (m/z), and the height indicates the abundance.

Percent Composition

The percentage of how much of an element is in a compound. Found by using the formula ((molar mass of element × element count) / (molar mass of compound)) × 100%. Essentially follows a similar pattern to stoichiometry, new/old.

Empirical Formula

Version of a composition that condenses the formula down to its simplest ratio. To find it, you can use the masses of each element (convert to moles, divide by smallest mole value, round or multiply to find whole number ratio) or the percentages of each element (‘assume you have 100g’ and use percentages as masses).

Molecular Formula

Version of a composition that demonstrates the stable/“normal” ratio of every element in the compound. Can be found by using the molar masses of each element (find the mass of the empirical formula, then compute molar mass/empirical mass to find your factor which you multiply all the subscripts by).

Mass Percent

The percentage of how much of an element or compound is in a mixture. Can be found by using the formula (mass of compound / mass of mixture) × 100%.

Contamination

Mixture with an unwanted chemical included. Typically caused by leftover reactants, accidental addition, etc. These can distort expected results in mass percent calculations; for instance, if mass percent ≠ percent composition, and it can be guessed based off a differing margin.

Coulomb’s Law

Proportional relationship of a charge’s attraction/repulsion showing how force increases as charge increases but decreases as radius increases. Expressed mathematically using F = k(Q₁Q₂/r), or relationally without the constant k using F ∝ Q₁Q₂/r (where F = Coulombic force of attraction/repulsion, Q₁ = Charge of protons in entire atom, Q₂ = Charge of a single electron, and r = radius between protons and electrons).

Orbital

Range of which an electron has the highest probability of existing at any given moment around the atom. There are s orbitals, p orbitals, d orbitals, and f orbitals. Each has 1 to 7 subshells.

Suborbital

Orientation of an orbital. For instance, s orbitals have one, and p orbitals have 3. Each can hold two electrons at a time.

Energy Level

Areas around the atom which 1 to 4 orbitals exist, detonated by principal quantum number and separated by nodes.

Aufbau Principle

Electrons fill whatever orbital requires the least amount of energy to fill first.

Hund’s Rule

Electrons fill each suborbital with one electron before adding the second. So, if an orbital has more than one suborbital, every suborbital will get one electron before a second is added to any of them.

Pauli Exclusion

No two electrons can have the same quantum number, so the electrons paired in a suborbital together must have opposite spins.

Valence Electron

Electron that sits on the outermost energy level of an atom, and are the easiest to remove from an atom.

Core Electron

Electron that is closer to the nucleus of the atom than its valence electrons. They have smaller radii than valence electrons, and they effect coulombic force by shielding valence electrons from the nucleus (Use Zeff instead of Z to represent protons in case this causes significant impact).