Common elements should be ions by default

[maxkfranz]

Currently, we prefer to list uncharged entities rather than charged one. This preference should be reversed for elements that are almost always ions in a user's paper:

• H 1+
• Na 1+
• K 1+
• Mg 2+
• Ca 2+
• Fe 3+ then 2+
• Cu 2+
• Zn 2+
• O 2-
• S 2-
• P 3-
• Cl 1-