Metal That Melts in Your Hand: A Review on Gallium

Have you ever heard of a metal that can melt right in your hands? Imagine holding something as solid as steel and having it start to liquefy in the palms of your hands. What is this extraordinary metal? This remarkable substance is called gallium, an element that counters our conventional understanding of metals. Gallium’s unique properties and characteristics continue to intrigue scientists and have greatly impacted the scientific world.

Gallium, represented by Ga on the periodic table, is a silvery-white metal with an atomic number of 31 and an atomic weight of approximately 69.723 amu. With a density of about 5.91 grams per cubic centimeter, gallium exhibits striking physical properties, notably its unusually low melting point and high boiling point. While it boasts a high boiling point of 2676 K (2403 °C or 4357 °F), what truly sets gallium apart is its remarkably low melting point of 302.9146 K (29.7646 °C or 85.5763 °F), just above room temperature. This makes gallium one of the few low-melting-point metals that is nontoxic compared to metals like francium, cesium, and rubidium.

Gallium was actually already known to exist even before it was ever discovered. Russian chemist Dimitri Mendeleev, the creator of the periodic table of elements, had identified this element as “eka-aluminum,” signaling that it would be the element below aluminum. Later in 1875, French chemist  Paul-Émile Lecoq de Boisbaudran discovered gallium using a spectroscope on zinc ores. When he discovered the new element, he decided to produce pure gallium through the electrolysis of gallium hydroxide in potassium hydroxide. Nowadays, gallium is known to be a versatile metal with unique properties.

But what makes gallium have such melting and boiling points? It all comes down to the atomic structure of gallium and the bonds between its molecules and atoms. Gallium possesses an unusual structure where each metal atom has one close neighbor at a small distance of about 2.43 A°. This structure makes gallium exist as more discrete diatomic molecules rather than a metallic structure, causing the melting point to be incredibly low. However, once gallium melts and turns into its liquid state, this structure no longer exists, making the boiling point high compared to its melting point. Gallium’s electron configuration is [Ar] 3d10 4s2 4p1. This means that the element has a partially filled 4p orbital, allowing for the formation of metallic bonds. In the liquid phase of the element, the metallic bonds contribute to its stability because of its strength. Metallic bonds tend to be stronger than other intramolecular forces such as ionic bonds, polar covalent bonds, and nonpolar covalent bonds. This ultimately contributes to Gallium’s high boiling point.

Because of its unique melting and boiling points, gallium has many applications within the world of science. Gallium has become a key element in semiconductor devices. Its high boiling point allows for the production of thin and uniform layers of gallium compounds, which is essential to maintain the performance and structure of the devices. This allows for devices such as light-emitting diodes, laser diodes, and high frequency transistors to be more reliable. Not only has gallium’s properties influenced the semiconductor industry, but it has also contributed to alloy development and thermometry. As a low melting point metal that is nontoxic and easily alloys with most other metals, gallium has long been used as a major component in low-melting alloys. In thermometry, gallium’s boiling point makes it an adequate substance to use in higher temperature thermometers and barometers because it will remain a liquid at high temperatures and is the most safe and environmentally friendly. Gallium also has applications in the pharmaceutical industry. For example, the compound gallium nitrate is used as a treatment for a disease that may cause bone tumors to form, hypercalcemia. Gallium also has implications for cancer treatment and infectious and inflammatory diseases though the radioisotope gallium-67. This isotope has been used as a nuclear medicine test to search for implications for these conditions.

Gallium stands as a testament to the diverse and unexpected behaviors found in the periodic table. Its ability to transition from a solid to a liquid at human touch exemplifies the groundbreaking nature of scientific discovery. Beyond its captivating physical properties, gallium continues to find practical applications in various fields, from electronics to medicine, highlighting its indispensable role in modern technology. I hope you learned something new! Keep a lookout for the next post!

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References

Faletto, J. (2019 Aug. 1). Gallium Is A Metal That Melts In Your Hands. Discovery. Retrieved September 16, 2022, from https://www.discovery.com/science/gallium-is-a-metal-that-melts-in-your-hands

Pederson, T. (2017 July 25). Facts About Gallium. Live Science. Retrieved September 16, 2022, from https://www.livescience.com/29476-gallium.html

TheMachineScience Core SME. (2022 June 7). The Boiling Point Of Gallium: A Comprehensive Guide. TheMachineScience. Retrieved September 16, 2022, from https://themachine.science/boiling-point-of-gallium/

Wang, H., Chen, S., Zhu, X., Yuan, B., Sun, X., Zhang, J., Yang, X., Wei, Y., Liu, Jing. Phase transition science and engineering of gallium-based liquid metal. Matter. Volume 5. Issue 7.

2022. Pages 2054-2085, ISSN 2590-2385. https://doi.org/10.1016/j.matt.2022.05.031