# How would you write the empirical formula of an ion?

How would you write the empirical formula of e.g. X2Y42-?

• Divide the charge too and write $XY_2^-$? – Anurag May 31 '18 at 14:21
• This seems like a really good question--I've never thought about it before. I recommend against closure. Since in the experimental analyses that involve the use of empirical formulas it is impossible to have large quantities of isolated ions, practically speaking it's not of very much use to define an empirical formula for an ion. – hBy2Py May 31 '18 at 19:13
• I think we should keep the question, if you allow me to digress into neutral things. Keep in mind that solid CrO3 forms Cr3O9 in the gas phase. – Nuclear Chemist Jun 30 '18 at 6:40