A single atom of an element has 21 neutrons, 20 electrons, and 20 protons, which elementis it?

An observation that requires measurement is called quantitative observable or qualitative

What term is applied to a scientist who studies ancient life, including animal and plant fossils a. anthropologist b. dendroclimatologist c. geophysicist d. paleontologist

Assume that 13.5 g solid aluminum (al) react with hcl to produce solid aluminum chloride (alcl3) salt and gaseous hydrogen (h2) at standard temperature and pressure.