Chemistry Lecture Notes: Electromagnetic Spectrum and Atomic Theory

Vocabulary flashcards covering atomic theory history, electromagnetic spectrum, photons, and light-matter interactions.

Dalton's atomic theory

Matter is composed of tiny particles called atoms; atoms are indivisible in chemical reactions and combine in whole-number ratios to form compounds.

Atom

The smallest unit of an element that retains its properties.

Plum pudding model

Thomson's model of the atom with a positively charged 'pudding' containing embedded electrons.

Nucleus

The dense, positively charged center of an atom containing most of its mass.

Rutherford gold foil experiment

An experiment showing atoms are mostly empty space with a tiny, dense nucleus.

Bohr model

Model proposing quantized electron orbits around the nucleus with fixed energy levels.

Quantum mechanics

The modern framework for describing electrons in atoms using wavefunctions, extending beyond Bohr's model.

Electromagnetic waves

Waves of oscillating electric and magnetic fields that travel through space; include visible light and other EM radiation.

Wavelength (lambda)

Distance between successive crests in a wave; inversely related to frequency.

Frequency (nu)

Number of wave crests passing a point per second; measured in hertz (Hz); inversely related to wavelength.

Speed of light (c)

Constant speed at which light travels in vacuum, about 3 x 10^8 m/s.

Photon

A discrete packet of light energy with energy proportional to its frequency.

Planck's constant (h)

A small constant (~6.6 x 10^-34 J·s) relating energy and frequency (E = hν).

E = hν

Energy of a photon is equal to Planck's constant times its frequency.

E = hc/λ

Energy of a photon equals Planck's constant times the speed of light divided by its wavelength.

Visible spectrum

Portion of the electromagnetic spectrum detectable by the human eye, roughly 400–750 nm.

Infrared (IR)

Wavelength region just longer than visible light; associated with heat and night-vision, relevant to climate.

Ultraviolet (UV)

Wavelength region shorter than visible light; higher energy; can damage DNA; sunscreen blocks it.

X-rays

High-energy electromagnetic radiation used for imaging; shorter wavelength and higher energy than UV.

Gamma rays

Extremely high-energy electromagnetic radiation from nuclear processes; highly penetrating and hazardous.

11-cis retinal

A retinal molecule in the eye that absorbs visible light and can undergo cis–trans isomerization to signal vision.

UV-Vis spectrometer

Instrument that measures how a sample absorbs or transmits UV and visible light to produce spectra.

Balmer series

Set of hydrogen emission lines in the visible region from transitions to n=2; lines include 656, 486, 434, 410 nm.

Emission lines

Discrete wavelengths emitted by excited atoms, resulting in a non-continuous spectrum.

Rydberg formula

Mathematical relation explaining hydrogen’s spectral lines; connects wavelengths to electronic transitions.