Mercury

Have you ever wondered what that shiny material is in a traditional thermometer? Well, it is a metal, Mercury. Yes, a metal with a liquid property, which makes it different from other metals in terms of physical as well as chemical properties. Today, we will be exploring the properties of this unique metal, Mercury. So let’s begin. 

1.0What is Mercury? 

Mercury is a liquid metal with an atomic number of 80, placing it in the transition metal category in the modern periodic table. It has fast-moving liquid droplets, with a striking, shiny silver colour, giving it its name as “quicksilver”. Mercury's chemical formula or symbol is Hg, derived from its Latin name hydragyrum, which also means "liquid silver." 

2.0Occurrence of Mercury

Mercury is a rare element in Earth’s crust, with a concentration of only about 0.08 parts per million (ppm). Just like other metals, mercury is not found in its native, pure form; instead, it is found in mineral ore. Mercury is mainly found in sulfide ores, also known as cinnabar (HgS). It is bright red in colour and extracted by the process of roasting, which is the heating of ore in the presence of oxygen. 

The process has the chemical reaction: 

$\mathrm{HgS}(s)+{\mathrm{O}}_2(g)\to \mathrm{Hg}(l)+{\mathrm{SO}}_2(g)$

In the reaction, when cinnabar is heated in air, oxygen reacts with the sulphur in the ore to produce sulphur dioxide, leaving behind the mercury in liquid or vapour form. 

The cinnabar deposits are mostly found in Spain, Italy, the USA (California and Nevada), Mexico, China, and Kyrgyzstan. 

3.0Electronic Configuration of Mercury 

In the Modern Periodic Table, mercury (Hg) is placed in Group 12 and Period 6, within the region where most metals are located. It is a transition metal, notable for being liquid at room temperature.

$[Xe]4f^{14}5d^{10}6s^2$

Explanation

• Mercury has an atomic number of 80, meaning it has 80 electrons and 80 protons. 
• It has a valency of 2, as the last shell or the valence shell of mercury has 2 electrons. 
• At the orbital level, it is completely filled with the 5d orbital and the 6s orbital. This is why it is more stable and less reactive than any other transitional metal.  

4.0Properties of Mercury

Physical Properties of Mercury 

Now let's learn about the physical characteristics of Mercury, which make it a metal:

• Mercury is the only metal that is liquid at room temperature and pressure.
• It is a reasonably good electrical conductor but a poor heat conductor, unlike most metals.
• The surface is silvery, smooth in texture, and thus lustrous, a common characteristic of metals.
• The density of mercury is very high (13.6 g/cm³ at 20℃), just like any other heavy metal. 
• Mercury also forms cations or positive ions to satisfy its valency, an intrinsic property of metals. 
• Although liquid at room temperature, mercury can be frozen at –39℃, which is also its melting point, and gives it a crystalline structure. 
• The boiling point of mercury is 356.7℃, meaning it vaporises at very high temperatures. 
• Mercury has a very high surface tension, causing it to form round droplets rather than spreading out.      
• Mercury is a volatile material, meaning it can slowly evaporate at room temperature, releasing toxic vapours harmful to the environment and human health.       

Chemical Properties of Mercury 

• Resistance to Moisture and Air: Mercury is a very weakly reactive metal, which helps prevent it from tarnishing in dry air. This allows it to remain shiny. 
• Oxidation Reaction: At high temperatures, mercury reacts with oxygen to form Mercury(II) oxide (basic in nature, like any other metallic oxide). 

$2\mathrm{Hg}(\mathrm{l})+{\mathrm{O}}_2(\mathrm{g})\to 2\mathrm{HgO}(\mathrm{s})$

• Reaction with Acids: 
• Mercury can not react with dilute acids; however, it reacts with concentrated sulfuric acids to form mercury sulfate and sulfur dioxide: 

$\mathrm{Hg}+2{\mathrm{H}}_2{\mathrm{SO}}_4\to {\mathrm{HgSO}}_4+{\mathrm{SO}}_2\uparrow +2{\mathrm{H}}_2\mathrm{O}$

• Mercury dissolves with aqua regia (HCl + HNO₃) to form mercuric chloride, like this: 

$\mathrm{Hg}+2\mathrm{HCl}+{\mathrm{HNO}}_3\to {\mathrm{HgCl}}_2+\mathrm{NO}+2{\mathrm{H}}_2\mathrm{O}$

• Alloy Formation: Mercury forms strong alloys (a mixture of two or more metals and a metal and non-metal) with other metals such as gold, silver, and zinc. Alloys of mercury are known as amalgams. 
• Reaction with Halogens: Mercury forms direct bonds with halogens or 17th group elements of the periodic table to form halides: 

$\mathrm{Hg}+{\mathrm{Cl}}_2\to {\mathrm{HgCl}}_2$

5.0Uses of Mercury 

The unique and fascinating properties of mercury make it usable in many fields of science and daily activities, such as: