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Multiple Choice
What is the correct chemical formula for the ionic compound formed between barium and bromine?
A
BaBr
B
Ba2Br2
C
BaBr2
D
Ba2Br
Verified step by step guidance
1
Identify the charges of the ions formed by each element: Barium (Ba) is an alkaline earth metal in Group 2, so it forms a cation with a charge of +2, written as $\mathrm{Ba^{2+}}$.
Bromine (Br) is a halogen in Group 17 and forms an anion with a charge of -1, written as $\mathrm{Br^{-}}$.
To form a neutral ionic compound, the total positive charge must balance the total negative charge. Since barium has a +2 charge and bromine has a -1 charge, you need two bromide ions to balance one barium ion.
Write the formula by placing the cation first followed by the anion, using subscripts to indicate the number of each ion needed to balance the charges: $\mathrm{BaBr_2}$.
Confirm that the total charge is zero: $+2$ from one $\mathrm{Ba^{2+}}$ and $2 \times (-1)$ from two $\mathrm{Br^{-}}$ ions sum to zero, indicating the formula $\mathrm{BaBr_2}$ is correct.