AP®︎ Chemistry: Unit 1 Flashcards

The mass of one mole of a substance, usually expressed in g/mol.

Add each element's atomic mass multiplied by its subscript in the chemical formula.

n = m/M, where m is mass in grams and M is molar mass.

Subscripts show atom ratios in a formula and determine particle-to-atom conversion relationships.

One mole contains 6.022 × 10^23 representative particles of a substance.

A particle's average mass in amu equals that substance's molar mass numerically in g/mol.

A conversion method using molar mass or Avogadro's number so units cancel correctly.

Atoms of the same element with different numbers of neutrons and different masses.

Peak position gives isotope mass; peak height or area gives relative abundance.

The proportion of each isotope in nature, usually written as a percent or decimal.

All isotope percentages for one element must add to 100%, or 1.00 as decimals.

The average lies closest to the isotope with the greatest natural abundance.

Match the spectrum’s isotope masses and weighted average to the element’s periodic-table atomic mass.

A graph from mass spectrometry showing isotope masses and relative abundances for one element.

The weighted average of isotope masses calculated using each isotope’s natural abundance.

The mass of a specific isotope, approximately equal to its protons plus neutrons.

Matter with a constant composition made of only one kind of particle.

Elements contain one type of atom; compounds contain two or more elements chemically combined.

Molecules are discrete covalent particles; formula units are lowest whole-number ratios in ionic compounds.

A pure compound always contains the same elements in the same mass ratio.

The lowest whole-number ratio of atoms of each element in a compound.

Assume 100 g, convert each element to moles, divide by the smallest, then multiply to whole numbers.

The lowest whole-number ratio of ions used to represent an ionic compound; counted as the representative particle for ionic substances.

The percent of a compound's total mass contributed by each element, found by dividing the mass of each element by the total mass and multiplying by 100%.

A pure substance has one type of particle; a mixture has two or more in variable proportions.

Homogeneous mixtures are uniform throughout; heterogeneous mixtures have visibly nonuniform composition.

Use counts and types of particles shown to determine composition, relative amounts, and whether a sample is pure.

Separates liquid mixture components by differences in boiling point through vaporization and condensation.

Separates insoluble solids from liquids using a porous barrier that traps larger particles.

Separates mixture components by different attractions to a stationary phase and a mobile solvent.

The stationary phase stays fixed; the mobile phase moves and carries substances past it.

More polar substances stick more to polar silica, while less polar substances travel farther with nonpolar solvent.

The distance traveled by a component divided by the distance traveled by the solvent front.

Uses element masses or percentages to find simplest whole-number atom ratios and assess purity.

Electrostatic force is proportional to charge product and inversely proportional to distance squared.

Shells are energy levels; subshells are s, p, d, f; inner electrons are core, outer are valence.

s holds 2 electrons, p 6, d 10, and f 14.

Electrons fill the lowest-energy orbitals available before occupying higher-energy orbitals.

An orbital can hold at most two electrons, and they must have opposite spins.

Electrons occupy equal-energy orbitals singly before any pairing occurs.

The lowest-energy arrangement of an atom's or ion's electrons among orbitals.

Use the previous noble gas in brackets, then write only the remaining outer subshells.

A box-and-arrow model showing orbital occupancy and electron spins in each subshell.

Add electrons for anions and remove highest-energy outer electrons for cations.

Atoms contain protons and neutrons in the nucleus and electrons outside it.

A technique that measures electron binding energies by ejecting electrons with high-energy photons.

The energy required to remove an electron from an atom, ion, or subshell.

Assign peaks to subshells by binding energy and use peak sizes to count electrons.

Photons eject electrons only if they provide enough energy to overcome the electrons' binding energies.

A graph where each subshell forms a peak whose position shows binding energy and height shows electron count.

Electrons closer to the nucleus have higher binding energies than valence electrons because attraction is stronger.

Recurring patterns in element properties caused by repeating valence electron configurations.

Periods are rows with the same occupied shells; groups are columns with similar valence electrons.

Elements in the same group have similar outer electrons and therefore similar chemical behavior.

Electrons occupy energy levels around the nucleus, with outer levels farther away and more shielded.

Electrostatic attraction increases with greater charge and decreases as distance between charges increases.

Decreases across a period and increases down a group because of charge and shell effects.

Cations are smaller than their atoms; anions are larger than their atoms.

Identify the large jump in values; electrons removed before it are the valence electrons.

Use an element's position, shells, shielding, and effective nuclear charge to estimate atomic properties.

Energy change when a gaseous atom gains an electron, generally more negative across periods and down groups less negative.

Inner electrons shield outer electrons from the full nuclear charge, so an electron experiences a reduced net positive attraction called effective nuclear charge.

The energy required to remove an electron from an atom; it increases with stronger nucleus-electron attraction, generally increasing across a period and decreasing down a group.

For main-group elements, the group number gives the number of outermost electrons.

Elements in the same group form similar compounds because they have the same valence electron pattern.

Group 1: +1, Group 2: +2, Group 13: +3, Group 15: -3, Group 16: -2, Group 17: -1.

Electrostatic attraction between oppositely charged ions formed after electron transfer.

Combine ions in the smallest whole-number ratio that makes the total charge zero.

Charged atoms or molecules are positive after electron loss and negative after electron gain.

Main-group atoms often gain or lose electrons to achieve a stable noble-gas-like valence shell.

The outermost electrons, usually in the highest principal energy level for main-group elements, that are involved in bonding; they can be identified from electron configuration by counting the outer s and p electrons.

An atom's ability to attract shared electrons in a bond; it generally increases across a period and decreases down a group and helps predict whether atoms gain, lose, or share electrons.

In successive ionization energies, each electron removed requires more energy, and a large jump after several removals indicates that all valence electrons have been removed; the number removed before the jump equals the number of valence electrons.