Atomic Structure, Periodic Trends, and Electron Configuration

Vocabulary flashcards covering periodic trends, energy levels, sublevels, orbitals, principles of electron configuration, historical atomic models, and electron configuration examples based on the lecture notes.

Atomic Mass

The average mass of the atoms of an element.

Atomic Mass Trend Across a Period

Generally increases from lighter to heavier elements across a period (e.g., Lithium at $6.99$, Sodium at $22.99$, and Magnesium at $24.31$).

Atomic Mass Trend Down a Group

Generally increases down a group or family (e.g., Sodium at $22.99$, Potassium at $39.10$, and Rubidium at $85.47$).

Atomic Radius Trend Across a Period

Decreases as you move across a period.

Atomic Radius Trend Down a Group

Increases as you move down a group or family.

Main Energy Levels ($n$)

Regions represented by the symbol $n$, where $n=1$ is closest to the nucleus, followed by $n=2$, $n=3$, and $n=4$ (maximum as of now).

Maximum Electrons Formula ($2n^2$)

Formula used to estimate the maximum number of electrons in a main energy level $n$ ($n=1 \rightarrow 2\text{ electrons}$, $n=2 \rightarrow 8\text{ electrons}$, $n=3 \rightarrow 18\text{ electrons}$, $n=4 \rightarrow 32\text{ electrons}$).

Sublevels

Specific sub-divisions within main energy levels designated by s-p-d-f notation, where higher main energy levels contain a greater number of possible sublevels.

Orbitals

Specific regions within sublevels where electrons are most likely to be found.

s Sublevel Capacity

Contains $1\text{ orbital}$ and can hold a maximum of $2\text{ electrons}$.

p Sublevel Capacity

Contains $3\text{ orbitals}$ and can hold a maximum of $6\text{ electrons}$.

d Sublevel Capacity

Contains $5\text{ orbitals}$ and can hold a maximum of $10\text{ electrons}$.

f Sublevel Capacity

Contains $7\text{ orbitals}$ and can hold a maximum of $14\text{ electrons}$.

Electron Configuration

The arrangement of electrons in the energy levels, sublevels, and orbitals of an atom, expressed using a main energy level number, a sublevel letter, and a superscript electron count (e.g., $1\text{s}^2$).

Aufbau Principle

States that electrons fill the lowest-energy orbitals first before moving to higher-energy orbitals ($1\text{s}$ fills before $2\text{s}$, $2\text{s}$ fills before $2\text{p}$, $2\text{p}$ fills before $3\text{s}$).

Pauli Exclusion Principle

States that an orbital can hold a maximum of $2\text{ electrons}$ only, and these electrons must have opposite spins.

Hund's Rule

States that when electrons occupy orbitals of the same sublevel, they fill each orbital singly first before pairing up.

Hund's Rule Orbital Diagram

Visual representation showing that electrons fill orbitals singly before pairing up with opposite spins.

Electron Configuration Mnemonic Chart

A diagonal arrow diagram showing the order in which sublevels fill up to their maximum electron capacities.

Dalton's Atomic Model

Proposed by John Dalton, describing the atom as a solid, indivisible sphere.

Postulates of Dalton's Atomic Model

All matter is made of atoms; atoms cannot be divided into smaller parts; atoms of the same element are alike; atoms of different elements are different; atoms combine in simple whole-number ratios to form compounds.

Limitation of Dalton's Atomic Model

Dalton thought atoms were indivisible, but later discoveries showed that atoms are actually made of smaller particles.

Electron Configuration of Hydrogen

With an atomic number of $1$, hydrogen has $1\text{ electron}$ and an electron configuration of $1\text{s}^1$.

Electron Configuration of Lithium

With an atomic number of $3$, lithium has $3\text{ electrons}$ ($2$ in $1\text{s}$ and $1$ in $2\text{s}$) giving an electron configuration of $1\text{s}^2 2\text{s}^1$.

Violations of Electron Configuration Rules

Writing $1\text{s}^2 2\text{p}^1$ violates Aufbau ($2\text{s}$ must fill before $2\text{p}$); writing $1\text{s}^3$ violates Pauli Exclusion (an orbital holds max $2\text{ electrons}$); pairing electrons early in a p sublevel violates Hund's Rule.