Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Determining charges of elements

  1. Apr 14, 2008 #1
    I know its a rather simple question but if you think about it, it requires much knowledge of d orbital. Is there an easy way a HS student can determine charges of elements using only a periodic table and no prior knowledge of orbitals? My old chem teacher said you could take the element and count backwards from the nearest noble gas, but this doesnt work all the time :(
  2. jcsd
  3. Apr 15, 2008 #2
    Well, the transition metals (the bulk of the table in the center) are weird and don't follow any particular easy rules. They also have the issue of having variable charges and such due to that d-orbital, so really, the only way I've ever seen to know them is to just memorize the common charges for each element. Chromium (IV), Chromium (VI), Mercury (II), Iron (III), etc. It's a bit of a pain.

    Through for the A-group elements (or Groups 1, 2, then 13 to 18 on your new-fangled Periodic Tables), you can tell charge based on what group they're in. Group 1 and 2 elements have +1 and +2 charges, then jumping across the trans-metals Boron's group has +3, Carbon's +4, and Nitrogen's +5. As suggested for the last two groups you can as a rule of thumb count back from the Noble Gases to guess the charge. The Halogens have -1 charges, the Chalcogens (Oxygen's group) are -2. Period Law is fun, but complicated at times.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook