What is the formula of a compound formed from the ions M1+ and X3-?
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You put the cation (positive ion) first, followed by the anion (negative ion).
MX
Next, you just switch their charges. It would take three M1- to combine with one X3- to form a neutral ionic compound.
M3X
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If they both have the same number charge, as say M2+ X2-, then you would just write.
MX
MX
Next, you just switch their charges. It would take three M1- to combine with one X3- to form a neutral ionic compound.
M3X
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If they both have the same number charge, as say M2+ X2-, then you would just write.
MX
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OK. The M1+ ion has lost one electron and the X3- has added 3 electrons. In order to achieve electrical neutrality in the final compound the # of negatives has to be balanced by the # of positives so you would have 3M's for each X..therefore the formula would be M3X.
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Using the criss cross method, the formula would be M3X
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M3X