What element has 12 protons 12 neutrons and 11 electrons

In a sample of oxygen gas at room temperature, the average kinetic energy of all the balls stays constant. which postulate of kinetic molecular theory best explains how this is possible?

Which type of orbits are found in the principal energy level n = 2 a - s b - s, f c - s, d d - s, p e - s, p, d

Write the empirical chemical formula of calcium with a mass percent of 38.8, phosphorus with a mass percent of 20.0, and oxygen with a mass percent of 41.3.