what is the charge of a PHOSPITE ?

and how do i write it?

phosphate = PO4-3

phosphite = PO3</-3

Here is a good site for all of the polyatomic ions, including phosphite ion.
(Broken Link Removed)

phosphite should be PO3-3

okay then, what is calcium phospite?

Ca3(PO3)3 in my book. However, to be fair about it, I looked on the web AND in The Merck Index and found CaHPO3 and it was labeled calcium phosphite. Technically, however, that should be called calcium hydrogen phosphite

The charge of a phosphite ion (PO3^-3) is -3.

To determine the charge, we need to look at the valence electrons of each atom in the ion. Phosphorus (P) is in Group 15 of the periodic table, so it has 5 valence electrons. Oxygen (O) is in Group 16, so each oxygen atom has 6 valence electrons.

In a phosphite ion, there are three oxygen atoms bonded to one phosphorus atom. Phosphorus typically forms three bonds, so it shares one valence electron with each oxygen atom. This results in the phosphorus atom having a +3 charge from having lost three valence electrons, while each oxygen atom has a -2 charge from gaining two valence electrons. Since there are three oxygen atoms, the total charge of the ion is (-2) * 3 = -6.

Since the overall charge of the phosphite ion is -6, it needs to balance out to obtain a neutral species. Therefore, the charge of the phosphite ion is -3 (-6/2).

To write the charge, you can use a superscript after the chemical symbol for the element. For example, the chemical symbol for the phosphite ion is written as PO3^-3, where the -3 represents the charge of the ion.