Week 2:   review of "Elements , Compounds, and Mixtures" website---

Very helpful to see these definitions again (last time was probably 1983)-- good to know compounds can't be busted apart physically, but mixtures can.... a compound does something different than its individual parts do....but mixtures retain many of the properties of their components.....good definitions all around, and pleasing graphics with the little Joan Miro-esque doodles, and the bouncing around argon atoms, nitrogen and water molecules......

Element of the Week: Calcium (Ca)

Atomic number (# of protons/electrons) is 20, #of neutrons is 20.

It's in the Alkaline Earth classification....has a cubic crystal structure....4 energy levels, and a silvery color!   It was discovered by Sir Humphrey Davy in 1808. The name comes from the Latin for lime= calcis. It is used for life forms for bones and shells, and comes from chalk , limestone, and marble.