Syllabus     |   |     Next Section

Learning Plan

  1. Watch the video on writing the formula for ions.

  2. Review Essential Information.

  3. Correctly write the forumula for ten ions in a row!

Once you get ten in a row, return to the Syllabus or continue to the next section (Types of Compounds).

Essential Information

Keys for Single Element Ions (e.g. Sodium ion):
  • Write the element symbol from the Periodic Table.
  • Find the charge for the element using the Periodic Table.
  • Write the charge as a superscript above and to the right of the element symbol.
For Single Element Ions of Transition Metals
  • Write the element symbol and then write ionic charge based on the Roman Numeral in the name. For example, the Iron (III) ion would be Fe3+.
  • You'll also want to do this for Pb, Sn as well.
Keys for Polyatomic Ions (e.g. NO3-,  PO43-,  NH4+):
  • Polyatomic ions have two or more elements. They usually have a negative charge.
  • Either memorize or look up on a Common Ion Table.


Elements or compounds with a + or – charge are called ions.

The + or – charge is because they gained or lost electrons.

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