Electron Configuration and Orbitals (Energy Levels)

A set of vocabulary flashcards covering energy levels, sublevels, orbitals, electron spin, and the electron configuration concepts from the lecture.

Principal quantum number (n)

The main energy level index for an electron; n = 1, 2, 3, … with energy increasing as n increases; each level contains sublevels.

Sublevel

Divisions within a principal energy level named s, p, d, f; the number of sublevels in level n equals n.

Orbitals

Regions within a sublevel where an electron is likely to be found; electron clouds derived from solving the Schrödinger equation.

s orbital

A sublevel with one orbital, spherical in shape; can hold up to 2 electrons; all s orbitals are spherical.

p orbital

A sublevel with three orbitals (px, py, pz); dumbbell shapes; can hold up to 6 electrons (3 orbitals × 2 electrons each).

d orbital

A sublevel with five orbitals; clover-shaped; can hold up to 10 electrons.

f orbital

A sublevel with seven orbitals; complex shapes; can hold up to 14 electrons.

Spin

Intrinsic angular momentum of an electron with two possible orientations: up and down.

Pauli exclusion principle

An orbital can hold at most two electrons with opposite spins; no two electrons share the same set of quantum numbers.

Aufbau principle

Electrons fill the lowest-energy sublevels first before occupying higher-energy sublevels.

Hund's rule

Within a sublevel, electrons occupy empty orbitals singly before pairing up; maximize unpaired spins where possible.

Electron configuration

The arrangement of electrons in an atom's orbitals, usually written as a sequence like 1s^2 2s^2 2p^6.

Valence electrons

Electrons in the highest occupied energy level; determine chemical properties and group placement.

Noble gas configuration

An electron arrangement with a full outer shell, giving stability and low reactivity (e.g., Ne: 1s^2 2s^2 2p^6).

Period

A horizontal row in the periodic table; corresponds to the principal energy level being filled.

Group

A vertical column in the periodic table; elements in a group share the same number of valence electrons.

s-block

The left block of the periodic table; outermost electron resides in an s sublevel (groups 1A-2A).

p-block

The right-hand block where the outermost electron resides in a p sublevel (groups 3A-8A).

d-block

The transition metals; outermost electrons occupy d sublevels.

f-block

The lanthanides and actinides; outermost electrons occupy f sublevels.

Electron cloud

The probabilistic region around the nucleus where an electron is likely to be found, not a fixed orbit.

Heisenberg uncertainty principle

You cannot know an electron's exact position and momentum simultaneously; location is probabilistic.

Schrödinger equation

The quantum equation used to determine the shapes and energies of orbitals; solving it yields orbitals.

4s vs 3d energy order

4s can be lower in energy than 3d, so 4s fills before 3d in many cases; explains some filling anomalies after Argon.

Maximum electrons per sublevel

s holds 2 electrons; p holds 6; d holds 10; f holds 14.

Maximum electrons in a given energy level

For n = 1: 2 electrons; n = 2: 8; n = 3: 18; n = 4: 32.

Orbital shapes reminder

s: sphere; p: dumbbells; d: clover; f: complex shapes.

Electron configuration notation

A compact way to describe occupation, such as 1s^2 2s^2 2p^6.

Valence electrons and groups

Elements in the same group have the same number of valence electrons, influencing chemical behavior.

Block description in periodic table

The blocks reflect the last occupied sublevel: s block (outermost s), p block (outermost p), d block (outermost d), f block (outermost f).