CHMY141 Lecture Notes: General Chemistry Concepts (Vocabulary Flashcards)

Vocabulary flashcards covering key chemistry concepts from the lecture notes.

Atom

The fundamental unit of matter; the basic unit of an element, consisting of a nucleus of protons and neutrons with electrons surrounding it.

Element

A pure substance made of only one kind of atom; cannot be broken into simpler substances by chemical means.

Compound

A pure substance composed of two or more elements in fixed proportions; can be broken down into elements by chemical means.

Mixture

A combination of two or more substances that retain their own properties; can be homogeneous or heterogeneous.

Homogeneous mixture

A mixture with uniform composition throughout, appearing the same in every part (a solution).

Heterogeneous mixture

A mixture with nonuniform composition; different parts can have different properties or compositions.

Physical change

A change that alters a substance without changing its chemical identity (no new substances formed).

Chemical change

A process that converts substances into new substances with different properties and compositions.

Density

Mass per unit volume; a measure of how tightly matter is packed (e.g., g/mL or g/cm³).

Mass

The amount of matter in an object, typically measured in grams.

Volume

The amount of space occupied by a substance, typically measured in liters or milliliters.

Uncertainty

Doubt in a measurement caused by instrument limitations or variability; represented by the last significant digit.

Significant figures

Digits in a measurement that carry meaningful information about precision, including all certain digits plus the first uncertain digit.

Exact numbers

Numbers with unlimited significant figures (e.g., counting items, defined quantities, certain conversion factors).

Scientific notation

A way of expressing numbers as a × 10^n to simplify writing very large or very small values.

Conversion factor

A ratio equal to 1 used to convert between units (e.g., 1 inch = 2.54 cm).

Atomic number (Z)

The number of protons in an atom; determines the identity of the element.

Mass number (A)

The total number of protons and neutrons in the nucleus.

Isotope

Atoms of the same element (same Z) with different numbers of neutrons (different A).

Ion

An atom or molecule with a net electric charge due to loss or gain of electrons.

Cation

A positively charged ion formed by the loss of one or more electrons.

Anion

A negatively charged ion formed by the gain of one or more electrons.

Molar mass

Mass of one mole of a substance, expressed in g/mol.

Avogadro's number

6.022 × 10^23 particles per mole.

Mole

Amount of substance containing Avogadro's number of entities (approximately 6.022 × 10^23).

Atomic mass unit (amu)

1/12 the mass of a carbon-12 atom; a standard unit for atomic masses.

Electron configuration

Arrangement of electrons among subshells in an atom, e.g., 1s² 2s² 2p⁶.

Aufbau principle

Electrons fill the lowest energy subshells before higher ones.

Hund's rule

Electrons will occupy empty degenerate orbitals singly before pairing up in the same orbital.

Pauli exclusion principle

No two electrons in an atom can have the same set of quantum numbers; each orbital holds at most two electrons with opposite spins.

Principal quantum number (n)

Quantum number that indicates the energy level and size of an orbital.

Angular momentum quantum number (l)

Quantum number that determines the orbital shape (l = 0 s, 1 p, 2 d, 3 f).

Magnetic quantum number (m_l)

Quantum number that determines the orientation of an orbital in space.

Spin quantum number (m_s)

Quantum number that specifies the spin orientation of an electron (+1/2 or -1/2).

s orbital

A spherical orbital (l = 0) surrounding the nucleus.

p orbital

Dumbbell-shaped orbitals (l = 1) with two lobes.

d orbital

Orbitals with more complex shapes (l = 2) often with four-lobed patterns.

f orbital

Even more complex orbitals (l = 3) with multiple lobes.

Bohr model

Early atomic model with electrons in fixed circular orbits; explains hydrogen spectra but has limitations.

Schrödinger equation

Quantum mechanical equation used to determine energies and wavefunctions of electrons; yields orbitals as probability densities.