Question

what is the formula of calcium bromide?
a) ca₂br₂
b) ca₂br
c) cabr₂
d) cabr

Explanation:

Step1: Determine the charge of calcium ion

Calcium (\(Ca\)) is in Group 2 of the periodic table. So, the calcium ion has a charge of \(Ca^{2+}\) (it loses 2 electrons).

Step2: Determine the charge of bromide ion

Bromine (\(Br\)) is in Group 17 of the periodic table. The bromide ion has a charge of \(Br^{-}\) (it gains 1 electron).

Step3: Use the criss - cross method

To form a neutral compound, the number of positive and negative charges must be equal. For \(Ca^{2+}\) and \(Br^{-}\), we need 2 \(Br^{-}\) ions to balance the \(2+\) charge of one \(Ca^{2+}\) ion. Using the criss - cross method (the magnitude of the charge of one ion becomes the subscript of the other ion), the formula is \(CaBr_{2}\).

Answer:

C. \(CaBr_{2}\)