Determine the number of protons neutrons and electrons in an isotope that has 21 neutrons and a mass number of 40

How many grams of oxygen gas are contained in a 15 l sample at 1.02 atm and 28°c? show your work.

The bond energy for the van der waals bond between two helium atoms is 7.9×10−4ev. assuming that the average kinetic energy of a helium atom is (3/2)kbt, at what temperature is the average kinetic energy equal to the bond energy between two helium atoms

Using the first volume and temperature reading on the table as v1 and t1, solve for the unknown values in the table below. remember to use the rules of significant figures when entering your numeric response.