Note: This video is designed to help the teacher better understand the lesson and is NOT intended to be shown to students. It includes observations and conclusions that students are meant to make on ...

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Mrs Roberts: What do you think you're made of? Mr Spellman: Big question. Grit, determination, hard-working, handsome, charming, funny. Mrs Roberts: Well, I guess. But you're actually made of atoms.

An element's atomic number defines it. An element with 17 protons will always be chlorine. However an element's mass numbers can vary, which means that it can have different numbers of neutrons. So ...

All the elements in the Periodic Table are made from different atoms, and the structure of these atoms results in a gamut of phenomena from radioactive decay to nuclear power. When you purchase ...

Donald B. Sullivan, a physicist and chief of the time and frequency division of the National Institute of Standards and Technology, explains. When the cesium second was defined in 1967, it was based ...