Re: How do you write formulas like Na2Cl for oxidation # and elements

As you probably have discovered, a discussion of oxidation numbers and chemical formulas is not a short topic! Your best option is to use a high school or college chemistry textbook. Keep searching until you find one that makes sense to you!

Some things to keep in mind:

Oxidation numbers are really just a convenient fiction for keeping track of electrons--essentially electron bookkeeping. Assigning oxidation numbers is by-and-large an application of a set of rules.

These web sites have good tutorials on how to assign oxidation numbers:

Roanoke Valley Governor's School (Roanoke, VA), Advanced Chemical Topics
  www.chem.vt.edu/RVGS/ACT/notes/oxidation_numbers.html

ChemTutor
  www.chemtutor.com/redox.htm

Kiwi Web: Chemistry and New Zealand
  www.chemistry.co.nz/redox_oxi_aa.htm

The ChemTeam at Diamond Bar High School (Walnut, CA)
  dbhs.wvusd.k12.ca.us/Redox/Redox.html

The Electronics Workshop (a ThinkQuest project)
  library.thinkquest.org/10784/chem2.html

I did not search for tutorials on writing chemical formulas, but the web sites above have a great many additional tutorials.

In my search, I came across three good sources of general chemistry tutorials you might want to bookmark for further questions about chemistry:

ChemTutor
  www.chemtutor.com/

Nelson Chemistry Resource Page
  www.agt.net/public/alariv/nelson.htm

Wilton High School Chemistry Resources (Wilton, CT)
  w3.nai.net/~bobsalsa/tutorial.htm