Which of the following is the correct chemical formula for mercury(I) chloride?

• A. HgCl2
• B. HgCl
• C. Hg2Cl
• D. Hg2Cl2

Answer: (D)

Verified step by step guidance

1. Understand the oxidation state of mercury in mercury(I) chloride. Mercury(I) means mercury has a +1 oxidation state, but mercury(I) exists as a diatomic ion, \(\mathrm{Hg_2^{2+}}\), where two mercury atoms share a +2 charge together.
2. Recognize that the mercury(I) ion is \(\mathrm{Hg_2^{2+}}\), not just a single mercury ion. This means the formula must include two mercury atoms bonded together.
3. Determine the charge of the chloride ion, which is \(\mathrm{Cl^-}\) with a -1 charge.
4. Balance the charges between the mercury(I) ion and chloride ions. Since \(\mathrm{Hg_2^{2+}}\) has a +2 charge, you need two \(\mathrm{Cl^-}\) ions to balance the charge, resulting in the formula \(\mathrm{Hg_2Cl_2}\).
5. Confirm that the formula \(\mathrm{Hg_2Cl_2}\) correctly represents mercury(I) chloride, reflecting the diatomic mercury(I) ion and the two chloride ions needed for charge neutrality.