The key difference between mercuric and mercurous is that the term mercuric is used to describe compounds containing Hg(II) cations, whereas the term mercurous is used to describe compounds containing Hg(I) cations.
Mercury is a metallic chemical element. It is a liquid metal at room temperature. Mercury polycation is a term used to name the polyatomic cations of mercury chemical element. The most common examples are mercuric cation and mercurous cation.
CONTENTS
1. Overview and Key Difference
2. What is Mercuric
3. What is Mercurous
4. Side by Side Comparison – Mercuric vs Mercurous in Tabular Form
5. Summary
What is Mercuric?
The term mercuric means, “containing Hg(II) cations”. We can give the chemical formula of this cation as Hg2+. Therefore, the mercuric cation has a +2 net positive charge. Also, we can say that its oxidation number is 2 (or, more precisely II). It is a divalent cation. There are different compounds containing this cation. These chemical compounds are named using the prefix “mercuric”—for example, mercuric chloride. We use different names to recognize this cation, e.g. mercuric ion, mercuric cation, mercury ion (Hg2+), mercury(II) ion, mercury (+2), etc. The molecular weight of this cation is 200.59 g/mol.
The mercuric ion belongs to the class of inorganic chemical compounds that we can classify as homogeneous transition metal compounds. These compounds are inorganic compounds containing only metal atoms. Here, the largest atom is a transition metal atom.
Figure 01: Mercury Chemical Element
In the human body, mercuric ions can be detected in different biofluids such as urine, blood, cerebrospinal fluid, etc. In addition to those, we can observe mercuric ions in various food items such as cloves, spelt, hickory nut, winged bean, etc. However, mercuric chemical compounds are known to be toxic compounds.
What is Mercurous?
The term mercurous means “containing Hg(I) cations”. This is the best-known polycation of mercury. We can give the chemical formula of this cation as Hg22+. Here, the mercury atom has a formal oxidation number 1. Therefore, we can classify it as a monovalent cation.
This ion is considered as the first metal cation that was confirmed to form homogeneous transition metal compounds. Other than that, the prefix “mercurous-” is used to name chemical compounds containing this cation.
In aqueous solutions, the mercurous ion is stable. Here, it occurs in equilibrium with elemental mercury and mercuric ion. We can readily shift his equilibrium by adding an anion that can form an insoluble Hg(II) salt such as mercuric sulfide. This type of compound can cause the complete disproportionation of mercurous salt.
What is the Difference Between Mercuric and Mercurous?
The most common polycations of mercury are mercuric and mercurous cations. The term mercuric refers to the meaning, “containing Hg(II) cations” while the term mercurous refers to the meaning, “containing Hg(I) cations”. Therefore, the key difference between mercuric and mercurous is that the term mercuric is used to describe the compounds containing Hg(II) cations whereas the term mercurous is used to describe the compounds containing Hg(I) cations.
Below infographic shows more details of the difference between mercuric and mercurous.
Summary – Mercuric vs Mercurous
Mercury is a metallic chemical element. It can form different cations named collectively as polycations. Mercuric and mercurous are two such cations of mercury. The key difference between mercuric and mercurous is that the term mercuric is used to describe the compounds containing Hg(II) cations whereas the term mercurous is used to describe the compounds containing Hg(I) cations.
Reference:
1. “Mercurous Ion.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine, Available here.
2. “Mercury Polycations.” Wikipedia, Wikimedia Foundation, 24 Jan. 2020, Available here.
Image Courtesy:
1. “Mercury (element)” By Albedo-ukr – Image:Mercury_(element).gif (CC BY-SA 2.5) via Commons Wikimedia