Evaluation Methods. Several studies from around the world that have evaluated Incredible Years components meet the Promising Practices Network (PPN) criteria and have found Incredible Years to be a promising or proven program. These studies are listed below, by the component that was tested in the study.
The noble gases (arranged in order of increasing atomic weight) are helium, neon, argon, krypton, xenon and radon. Helium, neon and argon are the three noble gases with the lowest atomic masses. Helium, Neon, Argon. Helium, neon, and argon are the three lightest members of the noble  gases. Hydrogen is the lightest of all elements. According to the Periodic  Table, its atomic weight is 1.00794 u, even lighter than helium.
At a given temperature and pressure, the density of a gas is proportional to its molecular weight. In theory, the next lightest gas after helium would be borane, BHâ (13.8 amu) but it exists as a minor component in equilibrium with its dimer, BâHâ (27.6 amu) and canât be obtained as a pure gas. The true next lightest gases would be methane, CHâ (16 amu), ammonia, NHâ (17 amu), hydrogen fluoride, HF (20 amu), and neon (20.2 amu). Because nitrogen, oxygen, and fluorine are all diatomic, their molecular weights are 28, 32, and 38 atomic mass units, respectively, and they are therefore denser than neon.