General Chemistry: Atomic Structure, Quantum Mechanics, and Periodic Trends

A comprehensive vocabulary review set covering foundational concepts in chemistry, including measurement principles, atomic structure, quantum mechanics, quantum numbers, electron configurations, and periodic trends.

Electron Configuration

The shorthand notation describing how electrons are distributed among the various atomic orbitals in an atom.

Aufbau Principle

The rule stating that an electron occupies the lowest-energy atomic orbital available before filling higher-energy orbitals.

Hund's Rule

The principle stating that for a set of degenerate orbitals, the most stable electron arrangement maximizes the number of unpaired electrons with parallel spins to minimize electron-electron repulsions.

Pauli Exclusion Principle

The principle stating that no two electrons in the same atom can possess the exact same set of four quantum numbers ($n$, $l$, $m_l$, $m_s$).

Effective Nuclear Charge ($Z_{\text{eff}}$)

The net positive nuclear charge actually experienced by an electron in a multi-electron atom, accounting for shielding effects by inner core electrons.

Atomic Radius

The distance between the nucleus of an atom and its outermost valence electron shell.

Ionization Energy ($IE$)

The minimum energy required to completely remove $1\,\text{mol}$ of electrons from $1\,\text{mol}$ of gaseous atoms or ions in their ground state.

Core Electrons

Inner electrons in an atom that correspond to the electron configuration of the preceding noble gas and do not participate directly in chemical bonding.

Valence Electrons

Electrons residing in the highest energy level (highest principal quantum number $n$), which are involved in chemical bonding and reactivity.

Principal Quantum Number ($n$)

The quantum number ($n = 1, 2, 3, \dots$) designating the main energy shell, overall size, and distance of an orbital from the nucleus.

Angular Momentum Quantum Number ($l$)

The quantum number specifying the shape of an orbital subshell, with allowed integer values ranging from $0$ to $n - 1$ ($s = 0$, $p = 1$, $d = 2$, $f = 3$).

Magnetic Quantum Number ($m_l$)

The quantum number designating the three-dimensional spatial orientation of an orbital within a subshell, with allowed integer values from $-l$ to $+l$.

Electron Spin Quantum Number ($m_s$)

The quantum number specifying the intrinsic spin orientation of an electron, taking values of $+\frac{1}{2}$ or $-\frac{1}{2}$.

Degenerate Orbitals

Atomic orbitals that belong to the same subshell and possess the exact same energy level.

Atomic Orbital

A three-dimensional region of space surrounding the nucleus where there is a high probability of finding an electron, accommodating a maximum of two electrons.

p Orbitals

Subshell atomic orbitals characterized by an angular momentum quantum number $l = 1$, possessing a dumbbell shape with three orthogonal spatial orientations ($m_l = -1, 0, +1$).

Periodic Law

The principle stating that the physical and chemical properties of the elements are periodic functions of their atomic numbers.

Heisenberg Uncertainty Principle

The fundamental quantum principle stating that it is impossible to simultaneously determine both the exact momentum ($p$) and position ($x$) of a particle with certainty.

Isotopes

Atoms of the same element containing the same number of protons (same atomic number $Z$) but different numbers of neutrons, resulting in different mass numbers ($A$).

Average Atomic Mass

The weighted average mass of all naturally occurring isotopes of an element, calculated from isotopic masses and their fractional natural abundances.

Mole ($\text{mol}$)

The SI base unit for amount of substance, defined as containing exactly $6.022 \times 10^{23}$ representative entities (Avogadro's number).

Molar Mass

The mass in grams of one mole of a substance ($g\,mol^{-1}$), numerically equivalent to its atomic or formula mass in atomic mass units ($\text{amu}$).

Accuracy

A measure of how close an experimental measurement or result is to the true or accepted value.

Precision

A measure of how closely multiple independent measurements of the same quantity agree with one another.

Significant Figures

All the meaningful digits recorded in a measured quantity, including all certain digits plus one final estimated or uncertain digit.

Matter

Anything that possesses mass and occupies physical volume in space.

Substance

A form of matter that has a definite, fixed composition and distinct, constant properties (either an element or a compound).

Element

A pure substance consisting of only one type of atom that cannot be broken down into simpler substances by chemical or physical means.

Compound

A pure substance composed of atoms of two or more different elements chemically united in fixed, definite mass proportions.

Homogeneous Mixture

A physical combination of two or more substances that possesses a uniform composition and appearance throughout.

Heterogeneous Mixture

A physical combination of two or more substances that lacks uniform composition and exhibits visually distinct phases.

Electrostatic Energy

A form of potential energy ($E_{\text{el}} \propto \frac{Q_1 Q_2}{d}$) resulting from electrostatic interactions between charged particles.

Density

An intensive physical property of matter defined as the ratio of mass to volume ($d = \frac{m}{V}$).