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Multiple Choice
Which of the following is the correct formula for the compound formed from Ca^{2+} and NO_3^{-} ions?
A
Ca_2NO_3
B
Ca(NO_3)_2
C
Ca_2(NO_3)
D
CaNO_3
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Verified step by step guidance
1
Identify the charges of the ions involved: calcium ion is Ca^{2+} and nitrate ion is NO_3^{-}.
Determine the ratio of ions needed to balance the overall charge to zero. Since Ca^{2+} has a charge of +2 and NO_3^{-} has a charge of -1, two nitrate ions are needed to balance one calcium ion.
Write the formula by placing the calcium ion first, followed by the nitrate ion with a subscript indicating the number of nitrate ions needed to balance the charge.
Use parentheses around the polyatomic ion nitrate (NO_3) when there is more than one nitrate ion to indicate that the subscript applies to the entire polyatomic ion.
The correct formula is therefore Ca(NO_3)_2, showing one calcium ion combined with two nitrate ions to form a neutral compound.