Which of the following is the correct chemical formula for barium hydroxide?

• A. Ba_2(OH)
• B. BaOH
• C. Ba_2O_2H_2
• D. Ba(OH)_2

Answer: (D)

Verified step by step guidance

1. Identify the ions involved: Barium is a metal from Group 2 of the periodic table, so it forms a cation with a charge of +2, written as \(\mathrm{Ba^{2+}}\).
2. Recognize the hydroxide ion: The hydroxide ion is a polyatomic ion with the formula \(\mathrm{OH^-}\) and a charge of -1.
3. Determine the ratio of ions needed to balance charges: Since barium has a +2 charge and hydroxide has a -1 charge, two hydroxide ions are needed to balance one barium ion, resulting in a neutral compound.
4. Write the chemical formula by placing the hydroxide ion in parentheses with a subscript 2 to indicate two hydroxide ions: \(\mathrm{Ba(OH)_2}\).
5. Verify that the formula is electrically neutral by confirming that the total positive charge (+2 from barium) balances the total negative charge (2 × -1 from hydroxide).