Medical Definition of PNEUMOTAXIC CENTER. : a neural center in the upper part of the pons that provides inhibitory impulses on inspiration and thereby prevents overdistension of the lungs and helps to maintain alternately recurrent inspiration and expiration. a neural center in the upper part of the pons that provides inhibitory impulses on inspiration and thereby prevents overdistension of the lungs and helps to maintain alternately recurrent inspiration and expiration.
Because of their uber-high stability, the noble gases are relatively unreactive. They have very high ionization energies and negligible electronegativities because they have no desire to gain or lose an electron.
The six noble gases are helium, neon, argon, krypton, xenon and radon. While they are all highly unreactive, the heavier elements of the group do sometimes form compounds under certain conditions. The inner electron shells of these elements form a sort of shield around the nucleus, allowing the gases to be ionized with sufficient energy.