In the writing of ionic chemical formulas, what factor is "crossed over" in the crossover rule? the value of each ion's charge the group number of each ion the number of each ion's valence electrons the atomic number of each ion

Ionic compounds are formed by the complete transfer of electrons between the atoms.  The atom which gains electron(s) forms anion whereas loss of electron(s) results in the formation of cation.  They are bonded to each other by electrostatic force of attraction between the negatively and positively charged atoms.

While writing the ionic chemical formula for binary ionic compound the rules are:

Hence, in the writing of ionic chemical formulas, the value of each ion's charge is "crossed over" in the crossover rule.

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explanation: