An atom contains 31 protons,39neutrons and 31 electrons. Identify the mass number of this atom

|using the periodic tablewarm-upuse the periodic table in the tools bar to answer the following questions.what elemental classification does oxygen belongto? done

A50.0 ml sample of gas at 20.0 atm of pressure is compressed to 40.0 atm of pressure at constant temperature. what is the new volume? 0.0100 ml 0.325 ml 25.0 ml 100. ml

How many moles of oxygen gas are produced from the decomposition of six moles of potassium chlorate