How many moles are in a 20.0 gram sample of calcium metal?

What material does not melt at any temperature

Which statement is true about this reaction? 14n+1h 15o it is a practical source of energy on earth. it occurs only outside the solar system. its product is heavier than each of its reactants. it shows the critical mass of an element.

The atomic number, or number, is the described as the number of in the nucleus of an chemical element.