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 octet rule. It is well known that the elements in group 8, the noble gases, are extremely unreactive. Examination of the electronic structures of these elements shows that the outer shells are full of electrons; they do not lack for electrons to fill the shells. None of the other elements has a filled outer shell.