Quantum Numbers, Electronic Configurations, and Periodic Trends

Vocabulary flashcards covering quantum numbers, periodic table classifications, orbital filling rules (Aufbau, Hund, Pauli), ion configurations, electron shielding, atomic radius, ionization energy, and effective nuclear charge.

Principal Quantum Number ($n$)

The quantum number representing the main energy level of an electron ($n = 1, 2, 3, 4$), with corresponding maximum capacities of $2$, $8$, $18$, and $32$ electrons.

Angular Momentum Quantum Number ($l$)

The quantum number defining the orbital shape, designated as $s$ (spherical), $p$ (dumbbell), and $d$ (cloverleaf).

Magnetic Quantum Number ($m_l$)

The quantum number specifying the spatial orientation of an orbital, taking values of $0$ for $s$; $-1, 0, 1$ for $p$; $-2, -1, 0, 1, 2$ for $d$; and $-3, -2, -1, 0, 1, 2, 3$ for $f$.

Electron Spin Quantum Number ($m_s$)

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

Period

A horizontal row of elements on the periodic table.

Main Group Elements

Elements categorized in Groups $1$, $2$, and $13$ through $18$ of the periodic table.

Transition Metals

Elements located in Groups $3$ through $12$ of the periodic table.

Lanthanides

A group of $15$ elements spanning from Lanthanum ($\text{La}$) to Lutetium ($\text{Lu}$) situated in the $4f$ block.

Actinides

A series of $15$ elements extending from Actinium ($\text{Ac}$) to Lawrencium ($\text{Lr}$) located in the $5f$ block, all of which are radioactive.

Alkali Metals

The reactive metallic elements found in Group $1$ of the periodic table, excluding hydrogen.

Alkaline Earth Metals

The metallic elements found in Group $2$ of the periodic table.

Aufbau Principle

The rule dictating that electrons fill the lowest available energy orbitals first before occupying higher levels.

Hund's Rule

The rule stating that when orbitals of equal energy (such as degenerate $p$ or $d$ orbitals) are available, electrons occupy each orbital singly before any orbital is doubly occupied.

Pauli Exclusion Principle

The principle stating that no two electrons in the same orbital can have the same spin; they must have opposite spins.

Cation Electron Configuration Rule

The procedure where positively charged ions lose electrons by removing them from the outermost shell first.

Anion Electron Configuration Rule

The procedure where negatively charged ions gain electrons by adding them to the outermost available subshell.

Electron Shielding

The effect where core electrons closer to the nucleus shield valence electrons from the nuclear pull, contributing to an increase in atomic size down a group.

Atomic Radius Trend

The periodic trend where the size of an atom increases moving down groups and to the left across periods, with Francium ($\text{Fr}$) having the largest radius.

Ionization Energy

The amount of energy required to remove an electron from a gaseous atom, which is an endothermic process represented by a positive sign ($$+$).

Ionization Energy Trend

The periodic trend where ionization energy increases moving up and to the right, with Helium ($\text{He}$) possessing the highest ionization energy and Group $1$ having the lowest.

Effective Nuclear Charge ($\text{ENC}$)

The net positive charge experienced by valence electrons, calculated using the formula $\text{ENC} = Z - S$, where $Z$ is the atomic number (protons) and $S$ is shielding core electrons; it increases across a period from left to right.