10 heaviest metals on earth based on density and atomic weight
The periodic table comprises a wide variety of elements, each with its own unique physical and chemical properties. Scientific research has discovered some elements that stand out due to their exceptional density and atomic weight. They make up the heaviest metals on earth and are used in various fields. So, do you know the heaviest metal in the universe? TUKO.co.ke spoke to Dr. Donata Adhiambo Odago, a chemistry teacher at Alliance High School, who gave an expert insight into the heaviness of metals based on density and atomic weight.
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Metals are natural elements in different shapes, sizes, and weights. Some are lightweight, like aluminium, while others are much heavier. You may think lead is the densest metal, but it may surprise you that other metals, like osmium, are twice as heavy as lead and exist naturally on earth.
What is the heaviest metal on earth?
The properties that determine the heaviness of a metal are its density, atomic weight, and atomic number. Density refers to the mass per unit volume and tells how much a material weighs. Here are the top 10 heaviest metals in periodic table according to Weight of Staff:
1. Osmium
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Which is the most heavy metal on earth? Osmium is the heaviest metal found on earth. Osmium's weight is twice that of lead metal. This toxic and extremely volatile element is also the most dense metal in the periodic table, with a 22.59 g / cm³ density.
It is a rare element that is extracted from platinum. And if you thought gold is valuable, then this hard, brittle metal with a bluish-white appearance is 30 times more valuable than gold because it is 1500 times rarer and has ten times more purity than gold. Osmium is used as an alloy in electrical contacts and fountain pens.
2. Iridium
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Iridium is a brittle, hard metal and the second heaviest metal in the periodic table, with a 22.56 g/cm³ density. This silvery-white metal is related to platinum, remains rust-resistant and can sustain high temperatures.
It is mostly extracted from South African, Russian, and Canadian nickel ores. The demand for Iridium mostly comes from the electronic, automotive, and chemical industries. It coats the electrodes in the Chlor- alkali process.
Its applications are mostly in spark plugs and electrodes, as it can withstand high temperatures. Since it's a rare toxic metal, it is mainly used as an alloy, such as osmium/iridium alloy, to make compass bearings.
3. Platinum
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With a density of 21.4 g/cm³, platinum is one of the heaviest metals on Earth. It is ductile, dense, malleable, unreactive, and one of the heaviest silver-white metals you can buy. Colombians first used the metal to produce artefacts.
It is around 60% denser than gold and is used in emission control vehicles, precious jewellery, glass, medicines, and anti-cancer agents. Pure platinum is less expensive than pure gold. The precious metal mostly mined in South Africa is tough and resistant to wear hence preferred for hard disk drives.
4. Rhenium
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Rhenium's density is 21.2 g / cm³, making it the fourth heaviest metal known. It is a tough metal that resists corrosion and has a high melting point, making it useful in applications for high temperatures.
This metal is often used as a component in superalloys for blades in turbine engines because it withstands the intense heat generated. Rhenium is also widely used as an electrical contact material due to its good electrical conductivity and resistance to wear.
5. Plutonium
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Plutonium is an actinide metal that became famous after the explosion of the world's first atomic bomb in Nagasaki, Japan. It has a silvery grey appearance that tarnishes and dulls when exposed to oxygen.
The radioactive metal emits a lot of thermal energy, which can also generate electricity. It is a perfect power source for devices that need to function without maintenance for about an average human's lifespan.
6. Gold
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Gold is one of the heaviest metals you can buy. Despite having a density of 19.30 g/ cm³, gold is a malleable and soft metal that can be beaten out to extremely thin sheets making it suitable for making jewellery, glass and anti-cancer agents.
Everybody is familiar with the bright yellow metal, but gold looks slightly reddish yellow in its purest form. It is used for creating corrosion-free electrical connectors in electrical devices like computers. Gold is the seventh heaviest element and more than 19 times heavier than water.
7. Tungsten
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Tungsten is a rare heavy metal mined naturally on Earth, often found with ores of other elements. It is a greyish-white, lustrous metal with the lowest vapour pressure in the periodic table.
With a density of 19.25 g / cm³, tungsten is known for its robustness and high density, which makes it the perfect to use in counterweights, tail ballasts in commercial aircraft, and ballast keels for yachts. It is also used in producing filaments for incandescent light bulbs at home, TV tubes and as X-ray targets.
8. Uranium
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Uranium, a silvery-grey actinide metal, is one of the heaviest metals on Earth. Uranium is a slow-decaying radioactive metal that provides the main heat source inside the Earth's core. With a high density of 19.10g / cm³, Uranium is commonly used in the military for nuclear weapons.
This radioactive metal is also used for power generation and to produce isotopes for medical and industrial purposes. Uranium fuel undergoes nuclear fission, releasing energy used to generate electricity. Supporters of nuclear power argue that uranium fuel is a clean and efficient source of energy that can help reduce carbon emissions.
9. Tantalum
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Tantalum has a density of 16.69 g/cm³ and is a silvery-coloured material with a high-melting point. The transition metal is known for its strength and is widely used in capacitors. Due to its high corrosion resistance, Tantalum is also used in medical instruments.
Tantalum capacitors are widely used in electronic devices due to their high stability. Tantalum is used in surgical instruments because of its biocompatibility and resistance to corrosion. Mining and extracting this metal is problematic as it can contribute to environmental degradation.
10. Mercury
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Mercury, a metal in liquid form at room temperature, is often called quicksilver for its silvery-white appearance. With a density of 13.53 g /cm³, Mercury is tenth on the heavy metals list. It weighs 13.6 times more than water in equal volumes, and materials like iron and lead can float on its surface.
This liquid metal is used in barometers, thermometers, and other scientific instruments; it is also excellent in conducting electricity. Before being determined as a toxic metal, mercury vapour was used in streetlights, advertising signs, and fluorescent lamps.
What makes a metal heavy?
Speaking exclusively to TUKO.co.ke, Dr. Donata Adhiambo Odago, a chemistry teacher at Alliance High School, explained that a metal is considered heavy based on its density. She said:
A metal is considered 'heavy' based on its density measured in grams per cubic centimetre. Heavy metals are characterised by a high mass number and/or a high density greater than 5 g/cm3. They are called 'heavy' because of their atomic number and mass number. In their atomic structure, they have more protons and neutrons in the nucleus, resulting in a high mass number. These are naturally heavy.
They are also considered 'heavy' because of atomic packing and structure. The atoms are densely packed, making them have a higher overall density. The way metals are arranged in the metallic crystal lattice affects how closely packed they are. Face-centred cubic and hexagonal close-packed structures allow for more dense packing of atoms, increasing the density of the metal.
At the same time, the chemistry teacher noted that other factors, including the composition of the isotopes and impurities, contribute to a metal being heavy.
Isotopes are atoms of the same element with the same atomic number but different mass numbers due to a difference in the number of neutrons. Some atoms exist in nature as a mixture of isotopes. A metal which has a heavier proportion of heavier isotopes will have a higher average mass number. This increases the density.
Another factor is impurities or alloying elements. The density of a metal can be increased through the addition of heavier elements as alloying agents. Tungsten alloys have a higher density than pure Tungsten caused by the addition of Rhenium or other dense elements.
Electron configuration and relativistic effect are other factors. Relativistic effect influences the behaviour of electrons in heavy elements like gold and lead. Relativistic effect affect bonding and packing in atoms, causing an indirect influence on density. An increase in atomic number causes the electrons on the innermost energy level to move faster due to the increased strength of positive nuclear attraction.
Advantages and disadvantages of heavy metals
According to Dr. Odago, heavy metals have a number of advantages and disadvantages due to their nature and use. She explained:
Heavy metals have a high density and mass number, making them useful for counterbalance, ballast and radiation shielding, e.g lead in X-ray vests and tungsten in aerospace counterbalance. Most heavy metals are also mechanically strong and withstand wear and tear. They are used for making tools, armour and high-stress components.
High melting points of elements such as tungsten make them sustainable for high-temperature environments such as rocket nozzles and filaments. Their dense atomic structure helps in absorbing gamma rays or X-rays, making them useful in medical or nuclear applications.
On the disadvantages, the chemistry teacher remarked:
Heavy metals are hard to transport; they increase fuel consumption in vehicles and planes. They are not good where lightweight and high mobility are needed. The majority of the heavy metals are also toxic (lead, mercury and cadmium) to human beings and the environment. Challenges of disposal and extra care are required when handling. Also, some heavy metals are rare (Platinum, Indium and Tungsten). They are expensive to mine and process. Due to their hard, dense and brittle nature, heavy metals are hard to machine or shape.
Misconceptions about heavy metals
The chemistry teacher noted that there are many misconceptions about heavy metals, which she explained in detail. Dr. Odago detailed:
There is a misconception that all heavy metals are toxic. The reality is that not all heavy metals are harmful. Some are required by human beings in trace form (Iron, Zinc and Copper). Also, some heavy metals like gold and platinum are not toxic in typical exposure levels. Some lighter metals like Aluminium and Berillium can be highly toxic.
Also, the term heavy metal is 'loosely' defined and misused. It is not a Scientific classification. Another misconception is that heavy metals are only harmful through ingestion. The truth is that they can be dangerous through inhalation (e.g lead dust), skin contact or even pre-natal exposure; mercury vapour and lead paint are good examples.
Similarly, natural does not mean safe. Heavy metals like arsenic, lead and cadmium occur naturally in soil and water, but natural sources can still be dangerous. Arsenic found in groundwater has caused massive health issues in places like Bangladesh. There's also a misconception that chelation therapy is a safe and effective detox for everyone. Chelation therapy is only medically appropriate in cases of heavy poisoning. Using it without a diagnosis can cause serious harm by stripping the body of essential minerals.
Heaviest metals on earth - Wrapping up
The heaviest metals on earth are rated based on factors such as density, atomic weight, and atomic number. These metals have various applications depending on their unique properties. Some of them metals are toxic but are found naturally on earth.
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