Which of the following is the composition of an isotope of calcium (atomic number 20)?

When a scientific theory has been tested and proved by the scientific community, it becomes a law

Alidded glass container is filled with a colored gas. after a period of time, it is observed that the gas is uniformly spread throughout the box and that the movement has slowed considerably. next, a warm iron plate is carefully placed under the box. why is there resumed movement of the gas in the container?

Calculate the percent composition by mass of each element in al(oh)3. use at least three significant figures.