If a 200 g sample of Radon-220 has a half-life of 55 seconds. How much material is left after 220 seconds?
A 12.5 g
B) 25 g
c) 55 g
D) 100 g

What is i fracture in the crust called when land move up, down or sideways

In 2002, the rare earth elements mine in mountain pass, california was closed because

As air becomes more dense, (select all that apply) o. air weighs less o. gas molecules are closer together o. air is colder o. air weighs more o. gas molecules are further apart o. air is hotter