Final answer:
The criss-cross method is a technique used in chemistry to write formulas for ionic compounds by criss-crossing the charges of ions to become subscripts of the opposite ion, ensuring electrical neutrality of the compound.
Step-by-step explanation:
Criss-Cross Method for Ionic Compounds
A student seeking assistance with criss-cross compounds is likely referring to the criss-cross method, which is a used to write formulas for ionic compounds. This method involves a series of steps:
- Write the symbol and charge of the cation (metal) first.
- Write the symbol and charge of the anion (non-metal) second.
- Criss-cross the numerical values of the ion charges to become the subscript of the other ion.
- Drop the signs of the charges.
For example, to write the formula for a compound formed from magnesium cation (Mg2+) and chloride anion (Cl-), we would criss-cross the charges to get MgCl2, where the subscript '2' indicates two chloride ions for every magnesium ion in the compound.
The criss-cross method is a straightforward way to ensure that the ionic compound is electrically neutral, with the total positive charge of cations equaling the total negative charge of anions.