Unit #5 COMPOUNDS

5.8 - Chemical Formulas for Ionic compounds

Write the chemical formula involving strontium and nitrate

Here we look at the charges on the ions.

strontium +2
nitrate -1

Drop the signs on the charges and determine the lowest common multiple (LCM) between "2" and "1".

For Sr+2 and NO3-, the LCM is

2 x 1 = 2

To determine the number of ions needed,

LCM / charge of ion = number of ions
Step 2:
Number of Sr+2 ions
Number of NO3- ions
2/2 = 1 Sr+2 ion

2/1 = 2 NO3- ions



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