Everythingin the universeis either matter or energy. All matter is made of combinations of about one hundred basic building blocks, the chemical elements on the periodic table. Going a step further and breaking these elements down to...

Article defines and explains compounds which are either ionic or covalent and molecules which are the simplest unit of a covalent compound. Molecules can be represented in many different ways.

It's hard enough to weigh something as itty bitty as atoms or molecules. Factor in that they're careening by faster than Jeff Gordon on steroids, and you get an idea what scientists are up against. Using comet particles from NASA's...

Learn interesting facts about nitrogen oxides, gases whose molecules are made of nitrogen and oxygen atoms and contribute to air pollution.

Learn about "hydrocarbons", chemical compounds whose molecules are made up entirely of carbon and hydrogen atoms.