Historical clue formulations

• The chloride in sodium chloride, e.g. — 2021-08-28
• I-, for one — 2020-11-13
• Bit of negativity? — 2020-06-14
• Particle with a negative charge — 2018-09-05
• Negative particle — 2018-05-17
• Atom with an electronic imbalance — 2018-01-26
• Fluoride, e.g. — 2016-05-05
• F-, H- or I-, but not G- — 2015-05-22
• It's written with a minus sign — 2014-01-17
• OH- or Cl-, chemically — 2013-12-11
• Bit of negativity? — 2013-01-06
• F-, for one — 2012-12-15
• OH- or Cl-, chemically — 2012-02-15
• Fluoride, e.g. — 2012-02-03
• Chloride or carbonate — 2009-07-15
• Negative particle — 2008-08-27
• Electrolysis particle — 2008-05-18
• It's negative — 2008-04-11
• Charged particle — 2007-05-22
• Electrolysis particle — 2007-03-03
• Electrolysis particle — 2006-09-10
• It's negative — 2005-10-14
• Part of an electrolytic exchange — 2005-06-18
• Negatively charged particle — 2004-06-28
• Electrolysis particle — 2004-03-05
• It's involved in electrolysis — 2003-04-12
• Cl-, e.g. — 2002-07-26
• Particle in electrolysis — 2002-03-18
• It has a negative charge — 2001-08-19
• Negative particle — 2000-03-15
• CH-, e.g. — 1999-12-22
• Negatively charged particle — 1999-05-31
• Charged atom — 1996-06-11
• Hydroxide particle — 1996-01-06
• Electrolysis particle — 1995-12-01
• Electrolysis particle — 1994-01-16