Historical clue formulations

• Krypton, for one — 2016-11-17
• "Noble" thing — 2016-11-06
• Noble at the end of a table? — 2016-05-20
• 21-Across, e.g. — 2014-12-12
• Noble one — 2014-05-10
• One highly unlikely to react — 2013-04-27
• Neon, for one — 2002-04-05
• Krypton, e.g. — 1997-07-04
• 37-Across, e.g. — 1996-11-08
• Krypton, for one — 1996-06-08