What is the mass of one mole of H2o

1) how many electrons are in each energy level of the following elements? a. he b. na c. na d. ne 2) how many valence electrons are percent in the following atoms? a. s b. mg c. be d. cl 3) which of the following elements are stable as atoms? a. he b. o c. cl d. ar if you are able to provide the work as to how you got the answers that would be greatly appreciated. : )

Calculate the molar mass of aluminum oxide (al2o3). express your answer to four significant figures.

About 3% of the water on earth is freshest. only about 40% of that freshwater is available for human use. why is so much freshwater unavailable for human use?