This stellar cloud column, made up of hydrogen gas and dust, is the birthplace for new stars.

Man is slightly nearer to the atom than the stars. From his central position he can survey the grandest works of Nature with the astronomer, or the minutest works with the chemist.

Arthur Eddington, British astronomer (1882-1944)

Perhaps we take chemistry for granted because nature makes everything look so easy. Every day, exploding stars eject new elements into the vastness of space. Extreme temperature and pressure create precious gemstones deep in Earth's belly. And on its surface, green plants transform carbon dioxide and sunlight into food for a living planet. Yet no one blinks an eye.

This image shows the atomic nucleus being surrounded by an electron cloud. The dense region indicates that the electron is more likely to be found there.

Welcome to the world of the atom, ruled by the tiny particles called electrons. They were discovered barely 100 years ago, and modern chemistry now knows enough about them to explain why glass breaks whereas rubber bounces. Understanding the properties of electrons fuels rockets into deep space, powers lightning-fast computer chips, and targets medical laser beams that destroy cancer cells. But it's been a long road.

For thousands of years, scientists labored under the misguided theories of the ancient Greek natural philosophers. Pseudoscientists called alchemists appeared in the Middle Ages, promising chemical elixirs that would cure all disease and lead to immortality. And as late as the 1850s, respected chemists experimented with the invisible (and nonexistent) substance called phlogiston, which had negative weight and caused materials to burn.

Elemental sodium dropped into water releases and ignites hydrogen gas in an impressive exothermic reaction.

Yet the longest road is often the most enlightening. As we retrace this journey marked with countless wrong turns and dead ends, what jumps out of the story are not the mistakes, but, rather, how often the right answers were there all along. Beginning with the very nature of matter, we will examine the forces at work in the unseen chemical world.

These forces are powerful indeed. Atoms, the building blocks of all matter, are more than 99% empty space. Yet we cannot thrust a hand through a solid wall because the force between electrons causes them to repel each other. Sometimes, though, matter does interact. Chemical reactions occur, and bonds form and break all around us. To understand how and why this happens, we will learn about the nature of the elements, the rules that govern chemical behavior, and some of the broader laws and theories of modern chemistry.

It's a material world. Let's explore it.

1. Fool's Gold: From Alchemy to Chemistry
   1. What's the Matter?
   2. Describing Matter
   3. Classification of Matter
   4. It's Elementary
   5. Atoms and Their Structure
   6. Molecules
   7. Atomic Properties
2. Patterns in Chemistry
   1. The Periodic Table
   2. Chemical Families
   3. Electron Basics
   4. More Electron Basics
   5. Periodic Trends
   6. Periodic Table Games
3. Types of Chemical Bonding
   1. Atoms That Share: Covalent Bonds
   2. Fatal Attraction: Ionic Bonds
   3. Rules of the Atomic Playground: Polar Covalent Bonds
   4. Identifying Bonds
4. Models and Shapes of Molecules
   1. The Octet Rule: Eight Is Great!
   2. Bond Energy
   3. Molecular Geometry
   4. Electron Group Geometry
   5. Molecular Polarity
   6. Hydrogen Bonding
5. Chemical Names and Formulas
   1. Name That Compound!
   2. Monatomic Ions
   3. Binary Ionic Compounds
   4. Polyatomic Ions
   5. Binary Covalent Compounds
   6. Acids
6. The Mole
   1. Atomic Weight
   2. Molecular Mass
   3. Percent Composition
7. Chemical Equations and Reactions
   1. Significant Figures
   2. Writing Chemical Equations
   3. Balancing Equations
8. Reaction Types
   1. Combination and Decomposition
   2. Single and Double Replacement
   3. Combustion
   4. Precipitation
   5. Acid/Base
   6. Oxidation-Reduction
9. State and Phase Changes
   1. Melting Points of Solids
   2. Solid Crystal Shapes
   3. Boiling Points of Liquids
   4. Vaporization of Liquids
   5. Gases
10. It's a Gas!
    1. Gas Behavior
    2. Law of Partial Pressures (Dalton's Law)
    3. Boyle's Law
    4. Charles' Law
    5. Combined Gas Law
    6. Avogadro's Hypothesis
    7. Ideal Gas Law
    8. Maxwell's Kinetic Theory of Gases