This "online textbook" is designed to provide a thorough, in-depth treatment of this topic at the first-year college or advanced-HS levels, with a special focus on the underlying concepts.

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Click one of the six lesson titles immediately below on the left;
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1- Quanta: a new view of the world

The limits of classical physics

The quantum revolution

Radiation is quantized

The photoelectric effect

Matter and energy united

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Max Planck and Albert Einstein

2- Light, particles and waves

The language of light

Light a particle: the photon

Light as electromagnetic radiation

Spectra: interaction of light with matter

Wavelength of a particle

The uncertainty principle

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3- The Bohr atom

The atom before Bohr

Bohr's orbital model

Spectrum of a guitar string

Standing waves in the hydrogen atom

The hydrogen spectrum explained

Emission and absorption spectrum; Fraunhofer lines

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4- The quantum atom

The wave function and its physical meaning

Why doesn't the electron fall into the nucleus?

Quantum numbers of electrons in atoms

Electron spin and the Pauli exclusion principle

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5- Atomic electron configurations

Atoms that have only one electron

Effects of electron-electron repulsion

The Aufbau rules

The periodic table

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6- Periodic properties of the elements

How the periodic table is organized

The shell model of the atom

Effective nuclear charge

Sizes of atoms and ions

Ionization energies

Electron affinities


References and periodic table links

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Among the many sources the author drew upon, special mention should be made of Pimentel and Spratley’s Understanding Chemistry, S. Brush’s Introduction to Concepts and Theories in Physical Science, P. Atkin’s Quanta, P. Davies’ The Forces of Nature, and the inspired writing of Toulmin and Goodfield in The Architecture of Matter.