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Naming Ions (including Polyatomic Ions)

Elements or compounds with a  +  or β€“  charge are called ions.

The  +  or β€“  charge is because they gained or lost electrons.

Losing an electron makes them positive (cation). Gaining an electron makes them negative (anion).

For example,
write the formula for:
  • Ca2+
  • Cl-
  • CO32-

Practice: The key to success.

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Keys for Single Element Ions (like Na+ , Cl-,  Ca2+,  N3-):

  • To name positive ions (called cations) write the name as found on the Periodic Table and add the word 'ion'.
  • For the negative ions (called anions) use the name from the Periodic Table but replace the ending with β€˜ide’. Then add the word 'ion' .

For Single Element Ions of Transition Metals

  • Write the ionic charge (the +1, +2 ...) as a Roman Numeral surrounded by parentheses. For example, Fe3+ would be the Iron (III) ion.
  • You'll also want to do this for Pb, Sn as well.

Keys for for Polyatomic Ions (like NO3-,  PO43-,  NH4+):

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