Generally, the more empty the outer electron shell, the more reactive the element. Helium has two(2) electrons, and is thus full, all the other noble elements has eight(8) electrons in it's outer electron shell, so they are also full. *And for everyone's sake, krypton is not green, but colorless, and forms white crystals when solid.
(a) Jubilees was written between 153 B.C. and the year of Hyrcanus' breach with the Pharisees. (1) It was written during the pontificate of the Maccabean family, and not earlier than 155 B.C., when this office was assumed by Jonathan the Maccabee.
A special anniversary, usually divisible by 25. The Jubilee stamps refer to the 1935 Silver Jubilee issue of King George V. (n.) The joyful commemoration held on the fiftieth anniversary of any event; as, the jubilee of Queen Victoria's reign; the jubilee of the American Board of Missions.