Atomic Structure and Periodicity

A collection of key terms and definitions related to atomic structure and periodicity for exam review.

Electromagnetic Radiation

A way energy travels through space, characterized by wavelength, frequency, and speed.

Wavelength (λ)

The distance between two consecutive peaks or troughs in a wave.

Frequency (ν)

The number of waves (cycles) per second that pass a given point in space.

Planck’s Constant (h)

A fundamental constant (6.626 × 10^-34 J·s) used to describe the quantization of energy.

Photoelectric Effect

The phenomenon where electrons are emitted from a metal surface when light strikes it.

Quantum Mechanics

A branch of physics that describes the behavior of matter and energy at atomic and subatomic scales.

Quantum Number (n)

An integer that specifies the energy level of an electron in an atom.

Bohr Model

A model of the hydrogen atom proposing that electrons travel in circular orbits at fixed distances from the nucleus.

Wave Function (Ψ)

A mathematical description of the quantum state of a system, giving probabilities of finding particles.

Heisenberg Uncertainty Principle

A principle stating that the position and momentum of a particle cannot be simultaneously known to arbitrary precision.

Orbital

A region in space where there is a high probability of finding an electron.

Electron Spin Quantum Number (ms)

A quantum number that describes the intrinsic angular momentum of an electron, with possible values of +1/2 or -1/2.

Pauli Exclusion Principle

The principle stating that no two electrons in the same atom can have identical sets of quantum numbers.

Ionization Energy

The energy required to remove an electron from a gaseous atom or ion.

Electron Affinity

The energy change when an electron is added to a gaseous atom, often resulting in the formation of an anion.

Atomic Radius

The distance from the nucleus of an atom to the outer boundary of the surrounding cloud of electrons.

Valence Electrons

Electrons in the outermost principal quantum level of an atom that participate in chemical bonding.

Core Electrons

Electrons in an atom that are not in the outermost principal quantum level.

Aufbau Principle

An assumption that electrons fill atomic orbitals in order of increasing energy.

Hund’s Rule

Electrons will fill degenerate orbitals singly before pairing up in orbitals.

Polyelectronic Atoms

Atoms with more than one electron, which require more complex models to describe their electron configurations.

Periodic Table

A tabular arrangement of the chemical elements, organized by increasing atomic number, electron configurations, and recurring chemical properties.

Alkali Metals

Group 1A elements known for their high reactivity, low ionization energies, and tendency to lose one electron to form positive ions.