Possible Clues:

• Atoms with + or – symbols
• They can be indicated by a + or –
• N in radio comms.
• Plus and minus items
• Atoms having electrical charges
• Carbonium and others
• Charged more than one of the end of 26 down
• Ammonium particles, e.g.
• Charged with 17 across poles
• H+ and ClÖ