CH 301 Unit 1 Exam Review - Quantum Mechanics and Periodic Trends

Vocabulary practice flashcards covering quantum mechanics numbers, electron configurations, magnetism, periodicity principles, and periodic trends for CH 301 Unit 1 Exam 1.

Principal Quantum Number ($n$)

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

Angular Momentum Quantum Number ($l$)

The quantum number describing the subshell and three-dimensional shape of an energy level, taking integer values from $0$ to $n - 1$.

Magnetic Quantum Number ($m_l$)

The quantum number specifying the spatial orientation of an orbital shape, taking integer values from $-l$ to $+l$.

Spin Quantum Number ($m_s$)

The quantum number describing the intrinsic spin orientation of an electron, which can only be $+\frac{1}{2}$ or $-\frac{1}{2}$.

Aufbau's Rule

The rule dictating that electrons fill available orbitals in order of increasing energy, starting from the lowest energy orbital to the highest.

Hund's Rule

The principle stating that within degenerate subshells ($p$ and $d$ orbitals), electrons spread out by placing one electron in each orbital with parallel spins before any pairing occurs.

Pauli Exclusion Principle

The quantum mechanical principle stating that no two electrons in an atom can have the exact same set of four quantum numbers, limiting each orbital to a maximum of two electrons with opposite spins.

Shorthand Notation

An electron configuration method in which the electron core is abbreviated using the symbol of the previous noble gas in brackets, followed by the remaining outer-shell electrons.

Valence Electron Configuration Notation

A configuration format that explicitly lists only the outermost valence electrons of an atom (for example, $s^2\,p^4$ for sulfur).

Isoelectronic

A term describing atoms or ions that possess the exact same total number of electrons and identical ground-state electron configurations.

Paramagnetic

A characteristic of atoms or ions that possess one or more unpaired electrons, causing them to be attracted to a magnetic field.

Diamagnetic

A characteristic of atoms or ions in which all electrons are paired, resulting in no attraction to a magnetic field.

Effective Nuclear Charge (ENC)

The net positive nuclear charge experienced by an electron, calculated by subtracting the number of core shielding electrons from the total number of protons.

Electron Shielding

The electrostatic barrier created by inner-shell electrons that repels outer valence electrons and reduces the full positive charge they feel from the nucleus.

Atomic Radius

The distance from an atom's nucleus to its outer electron boundary, which increases down a group due to added shielding shells and decreases across a period due to increasing effective nuclear charge.

First Ionization Energy

The energy required to pull a valence electron away from an atom, producing a positively charged ion.

Islands of Stability

Periodic anomalies in ionization energy where full or half-filled subshells (such as $p^3$) exhibit greater thermodynamic stability than predicted by simple effective nuclear charge arguments alone.

Electronegativity (EN)

A measure of the tendency of an atom to attract electrons, which steadily increases across the periodic table diagonally toward fluorine.