Energy Configuration & Atomic Models

Flashcards covering key vocabulary from lecture notes on atomic energy configuration, historical and quantum models of the atom, electron properties, quantum numbers, orbitals, electron configurations, and related periodic table trends.

Bohr Model

A theoretical model of the hydrogen atom where electrons move around the nucleus in fixed, circular paths or orbits.

Orbit (Bohr Model)

A fixed, circular path (also called a 'shell') where an electron moves around the nucleus, similar to a planet orbiting the sun.

Shell (Principal Quantum Number, n)

Labeled 'n' (n=1,2,3…), representing the fixed orbits in the Bohr model, which dictate the energy level and size of the orbit.

Quantum Numbers

A set of four numbers (n, l, ml, ms) that completely describe the state and properties of an electron in an atomic orbital.

Principal Quantum Number (n)

Determines the main energy level or shell of an electron; relates to the energy and average size of the orbital.

Secondary (Angular Momentum) Quantum Number (l)

Determines the shape of an orbital (subshell); l=0 for s, l=1 for p, l=2 for d, and l=3 for f orbitals.

Magnetic Quantum Number (m_l)

Determines the orientation of an orbital in three-dimensional space.

Spin Quantum Number (m_s)

Describes the intrinsic angular momentum of an electron, which can have values of +1/2 or -1/2, indicating its spin direction.

Sub-level

Designations s, p, d, and f, corresponding to different orbital shapes defined by the 'l' quantum number.

De Broglie Model

A model that views electrons as having both particle-like properties (mass + velocity) and wave-like properties.

Standing Wave

The behavior of an electron with mass and speed when bound inside an atom, existing in specific, stable wave patterns around the nucleus (not orbiting).

Wavelength (λ)

The distance between two consecutive corresponding points (e.g., peaks or troughs) on a wave.

Frequency (ν)

The number of complete cycles or oscillations that pass a given point per unit of time (measured in Hz or s⁻¹).

Amplitude

The maximum displacement or distance moved by a point on a vibrating body or wave from its equilibrium position.

Node (Wave)

A point or region in a standing wave where the amplitude is always zero, meaning the probability of finding an electron there is zero.

Constructive Interference

Occurs when two or more waves combine in such a way that their amplitudes add up, resulting in a stronger wave.

Destructive Interference

Occurs when two or more waves combine such that their amplitudes cancel each other out, resulting in a smaller amplitude or a node.

Heisenberg's Uncertainty Principle

States that it is fundamentally impossible to precisely determine both the exact position and the exact momentum (or energy) of an electron at the same time.

Schrödinger Equation

A mathematical equation that describes the wave function and corresponding energy levels of electrons in atoms, foundational to quantum mechanics.

Wave Function (Ψ)

A mathematical description of the state of an electron in an atom, which describes the shape and energy levels of the electron's wave-like behavior.

Atomic Orbital

A three-dimensional region around the nucleus where there is a high probability of finding an electron, as defined by quantum mechanics.

Probability Density (Ψ²)

The square of the wave function, which represents the probability of finding an electron at a particular point in space within an orbital.

Electron Density

A graphic representation (e.g., dot diagram or cloud) showing the probability distribution of electrons in an orbital; denser areas indicate higher probability.

Node (Atomic Orbital)

A region within an atomic orbital where the probability of finding an electron is zero.

Spherical Node (Radial Node)

A concentric spherical region within an orbital where the electron density is zero, typically found in s orbitals.

Angular Node (Nodal Plane)

A planar region within an orbital where the electron density is zero, often associated with p and d orbitals where a phase change occurs.

Boundary Diagram

A graphical representation that outlines the shape of an atomic orbital by enclosing the region where an electron is found with a high probability (e.g., 90%).

p Orbitals

Atomic orbitals characterized by two lobes on opposite sides of the nucleus, separated by a nodal plane (e.g., px, py, p_z).

d Orbitals

Atomic orbitals characterized by more complex shapes, typically four lobes (except for d_z²) and two nodal planes or conical nodes.

Nodal Plane

A plane passing through the nucleus in an orbital where the probability of finding an electron is zero.

Nodal Cones

Conical regions within the d_z² orbital where the probability of finding an electron is zero.

Degenerate Orbitals

Orbitals that have exactly the same energy level, such as the three p orbitals within a given subshell (e.g., 2px, 2py, 2p_z).

Aufbau Principle

States that electrons will first occupy atomic orbitals that have the lowest available energy levels before filling higher energy levels.

Ground State (Electron Configuration)

The electron configuration of an atom in its most stable, lowest possible energy state.

Hund's Rule

States that for degenerate orbitals (of equal energy), electrons will occupy each orbital individually with parallel spins before any orbital is occupied by a second electron.

Excited State

An electron configuration where one or more electrons occupy an orbital of higher energy than in the ground state, typically achieved by absorbing energy.

Electronic Configuration

The complete distribution or arrangement of electrons among the atomic orbitals of an atom or ion.

Spin Paired Electrons

Two electrons occupying the same orbital with opposite spins (+1/2 and -1/2), whose magnetic moments cancel each other out.

Pauli Exclusion Principle

States that no two electrons in an atom can have the exact same set of four quantum numbers; consequently, an atomic orbital can hold a maximum of two electrons, and they must have opposite spins.

Diamagnetic Material

A substance in which all electrons are spin-paired, resulting in a slight repulsion by an external magnetic field.

Paramagnetic Material

A substance that contains one or more unpaired electrons, causing it to be attracted by an external magnetic field.

Maximum Capacity of Subshells

The maximum number of electrons that can occupy each type of subshell: s (2), p (6), d (10), and f (14).

Maximum Capacity of Shells

The maximum number of electrons that can occupy a given principal shell 'n', calculated by the formula 2n².

s-block elements

Elements in Groups 1A and 2A of the periodic table, characterized by their outermost electrons occupying s orbitals.

p-block elements

Elements in Groups 3A to 8A of the periodic table, where the outermost electrons occupy p orbitals.

d-block elements (Transition Metals)

Elements in Groups 3-12 of the periodic table, characterized by the progressive filling of d orbitals.

f-block elements (Lanthanides and Actinides)

Elements typically placed below the main body of the periodic table, characterized by the progressive filling of f orbitals.

Valence Electrons

The electrons located in the outermost principal energy shell (highest 'n') of an atom, which are primarily involved in chemical bonding.

Core Electrons

The electrons in an atom that are not valence electrons; they are located in inner shells and are generally not involved in chemical reactions.

Ions

Atoms or molecules that have gained or lost one or more electrons, resulting in a net positive or negative electrical charge.

Cations

Positively charged ions, formed when an atom loses one or more electrons, typically from its outermost shell.

Anions

Negatively charged ions, formed when an atom gains one or more electrons, typically into its valence shell.

Octet Rule

The tendency of atoms to gain, lose, or share electrons in order to achieve a stable electron configuration with eight electrons in their outermost (valence) shell, similar to a noble gas.

Isoelectronic

Refers to atoms or ions that have the same electron configuration and thus the same number of electrons.

Half-filled d-orbitals

A particularly stable electronic configuration for d-block elements where each of the five d-orbitals is occupied by a single electron (e.g., d⁵ configuration).

Completely-filled d-orbitals

A particularly stable electronic configuration for d-block elements where all five d-orbitals are fully occupied by two electrons each (e.g., d¹⁰ configuration).