What percent of the universe's age is the first 400,000 years?

Compare and contrast the bohr model and the electron cloud models of the atom.

The famous scientist galileo galilei did several experiments with sloping planes, which he rolled metal balls down so that he could study motion. by changing the slope, he could study how the speed at which the ball rolled was affected. what was the independent variable in galileo's experiment? a. the speed of the ball b. the slope of the plane c. whether the ball moved d. what the ball was made of

Estimate the molar mass of the gas that effuses at 1.6 times the effusion rate of carbon dioxide.