Who was the first to propose the idea of atoms?

Name the element in group 17, period 2. (periodic table)

Ageologist determines that a sample of a mineral can't be scratched by a steel nail but can be scratched by a masonry drill bit. based on this information, the sample mineral has to be softer than a. orthoclase. b. fluorite. c. apatite. d. corundum.

In what environment would mineral formation caused by high pressures and high temperatures most likely occur?