Question

1. use the ionic charges with your crisscross rule to get the correct compound formula.
2. name the compound.

li + s
na + n
ca + br
al + p
li + cl
ca + f

Explanation:

Step1: Determine ionic charges

Li has a +1 charge, S has a - 2 charge. Using criss - cross rule, the formula is $Li_2S$ and it is lithium sulfide.

Step2: For Na and N

Na has a +1 charge, N has a - 3 charge. Using criss - cross rule, the formula is $Na_3N$ and it is sodium nitride.

Step3: For Ca and Br

Ca has a +2 charge, Br has a - 1 charge. Using criss - cross rule, the formula is $CaBr_2$ and it is calcium bromide.

Step4: For Al and P

Al has a +3 charge, P has a - 3 charge. Using criss - cross rule, the formula is $AlP$ and it is aluminum phosphide.

Step5: For Li and Cl

Li has a +1 charge, Cl has a - 1 charge. Using criss - cross rule, the formula is $LiCl$ and it is lithium chloride.

Step6: For Ca and F

Ca has a +2 charge, F has a - 1 charge. Using criss - cross rule, the formula is $CaF_2$ and it is calcium fluoride.

Answer:

$Li_2S$, lithium sulfide
$Na_3N$, sodium nitride
$CaBr_2$, calcium bromide
$AlP$, aluminum phosphide
$LiCl$, lithium chloride
$CaF_2$, calcium fluoride