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.
Iliad is the oldest surviving Greek poem, It was written by Homer between 800 and 700 B.C. The poem is about some events that took place in final years of Trojan war that took place between Greece and Troy. Odyssey which is a sequel to Iliad was also written by Homer. Not much is known about Homer.