Historical clue formulations

• 2, for He: Abbr. — 2024-01-12
• ___ time (never) — 2020-11-10
• Scandium's is 21: Abbr. — 2018-05-27
• Periodic table fig. — 2018-04-25
• What "This" refers to, in this puzzle's theme: Abbr. — 2017-10-10
• Md or Rn fig. — 2017-05-27
• 1 for hydrogen or 2 for helium: Abbr. — 2016-02-16
• "... ___ extra charge!" — 2015-05-17
• ___ extra cost — 2014-08-26
• 53 for I, e.g. — 2014-08-06
• "... ___ cost to you!" — 2014-04-07
• O's is one more than N's — 2014-03-29
• He's 2, for one — 2014-01-26
• It's 8 for O — 2014-01-03
• Fig. for I, O or U, but not A or E — 2013-12-28
• Stat. for Re, La or Ti — 2013-10-11
• Periodic table fig. — 2013-07-31
• W's is 74 — 2013-07-13
• ___ time (never) — 2013-03-25
• Figure on a table: Abbr. — 2013-01-19
• Zinc's is 30: Abbr. — 2012-03-26
• Periodic table info: Abbr. — 2012-03-07
• He's 2, say — 2012-01-21
• Am or Fm stat — 2011-08-13
• 6, for C — 2011-07-07
• ___ time (never) — 2011-03-20
• "___ extra cost!" — 2010-11-16
• Periodic table fig. — 2010-02-21
• ___ extra cost — 2010-01-26
• 8 for O, say — 2009-03-13
• 5 for B or 6 for C — 2009-02-01
• 80, for Hg — 2008-09-18
• It's 8 for O — 2008-05-31
• 13, for Al — 2007-12-09
• 79, for gold: Abbr. — 2007-09-04
• ___ extra cost — 2007-04-25
• 95 for Am or 100 for Fm: Abbr. — 2007-04-07
• Au's is 79 — 2007-04-04
• "___ cost to you!" — 2007-02-18
• ___ extra cost — 2006-07-24
• Periodic table fig. — 2006-06-27
• Fig. on a periodic table — 2006-06-08
• 27 for 56-Across, e.g.: Abbr. — 2005-12-18
• Chem. datum — 2005-11-19
• 79 for gold, e.g.: Abbr. — 2005-05-12
• "___ additional cost!" — 2005-03-14
• 79 for gold, e.g.: Abbr. — 2005-01-20
• Periodic table stat. — 2005-01-16
• "___ extra cost!" — 2005-01-05
• "___ extra cost!" — 2004-07-20