Chapter 4 Chemistry Study Guide: Radiant Energy and the Quantum-Mechanical Model

Vocabulary flashcards covering electromagnetic radiation, quantum theory, atomic spectra, Bohr's model, wave-particle duality, and the quantum-mechanical model of the atom.

Electromagnetic Radiation

A form of radiant energy that includes visible light, infrared, ultraviolet, X-rays, gamma rays, and radio waves, characterized by its amplitude, wavelength, frequency, and speed.

Amplitude

The height of a wave measured from its original point.

Wavelength ($\lambda$)

The distance between wave crests, typically measured in nanometers ($\text{nm}$).

Frequency ($\nu$)

A measure of how fast a wave oscillates, typically measured in Hertz ($\text{Hz}$).

Speed of Light ($c$)

The constant speed of electromagnetic radiation equal to $3.00 \times 10^8\,\text{m/s}$, related to wavelength and frequency by $\lambda = \frac{c}{\nu}$ or $\text{Speed of light} = \text{wavelength} \times \text{frequency}$.

Quantum

A discrete unit in which energy is emitted or absorbed, as proposed by Max Planck.

Planck's Constant ($h$)

The proportionality constant in the equation $E = h\nu$, equal to $6.6261 \times 10^{-34}\,\text{J}\cdot\text{s}$.

Photoelectric Effect

The phenomenon in which electrons are emitted from a metal surface when it is exposed to light of a specific frequency.

Photon

A discrete packet or particle of light proposed by Albert Einstein, carrying energy proportional to its frequency.

Wave-Particle Duality

The concept that light and matter exhibit both wave-like and particle-like properties.

Continuous Spectrum

A spectrum that displays all colors of visible light uninterrupted across a range of wavelengths.

Line Spectrum

A spectrum consisting of distinct colors emitted at specific, isolated wavelengths.

Atomic Emission Spectrum

A unique set of emitted frequencies characteristic of a specific element that acts like an elemental fingerprint.

Ground State

The lowest quantized energy level of an electron in an atom, corresponding to $n = 1$ in Bohr's model.

Excited State

An unstable higher energy state reached when electrons absorb energy before emitting light as they return to lower levels.

Matter Waves

The concept introduced by Louis de Broglie proposing that particles such as electrons exhibit wave-like behavior.

Heisenberg's Uncertainty Principle

The principle stating that it is impossible to simultaneously determine both the position and momentum of an electron.

Quantum-Mechanical Model

An atomic model that describes the probability of finding electrons in specific regions around the nucleus, represented as electron density clouds.

Atomic Orbital

A defined region in space around an atom's nucleus where electrons are likely to be found, with specific shapes and sizes corresponding to energy levels.

Principal Quantum Number ($n$)

A quantum number representing the main energy level of an electron, which can hold a maximum of $2n^2$ electrons.

Aufbau Principle

The electron configuration rule stating that electrons fill the lowest energy orbitals first.

Pauli Exclusion Principle

The rule stating that no two electrons in an atom can have the same set of quantum numbers, meaning each orbital can hold a maximum of two electrons with opposite spins.

Hund's Rule

The electron configuration rule stating that electrons remain unpaired until each orbital in a sublevel has one electron.