| Discovery date | 1875 |
| Discovered by | Paul-Émile Lecoq de Boisbaudran |
| Origin of the name | The name is derived from the Latin name for France, 'Gallia' |
| Allotropes |
|
Ga
Gallium
31
69.723
| Group | 13 | Melting point | 29.7646°C, 85.5763°F, 302.9146 K |
| Period | 4 | Boiling point | 2229°C, 4044°F, 2502 K |
| Block | p | Density (g cm−3) | 5.91 |
| Atomic number | 31 | Relative atomic mass | 69.723 |
| State at 20°C | Solid | Key isotopes | 69Ga |
| Electron configuration | [Ar] 3d104s24p1 | CAS number | 7440-55-3 |
| ChemSpider ID | 4514603 | ChemSpider is a free chemical structure database | |
Image explanation
The image reflects on puns relating to the origin of the element’s name. Lecoq de Boisbaudran named the element after France (‘Gaul’ in Latin) and also himself, since Lecoq, which means ‘the rooster’ translates to ‘Gallus’ in Latin. A silvery metallic rooster is shown on a background of an antique map of France.
Appearance
Gallium is a soft, silvery-white metal, similar to aluminium.
Uses
Gallium arsenide has a similar structure to silicon and is a useful silicon substitute for the electronics industry. It is an important component of many semiconductors. It is also used in red LEDs (light emitting diodes) because of its ability to convert electricity to light. Solar panels on the Mars Exploration Rover contained gallium arsenide.
Gallium nitride is also a semiconductor. It has particular properties that make it very versatile. It has important uses in Blu-ray technology, mobile phones, blue and green LEDs and pressure sensors for touch switches.
Gallium readily alloys with most metals. It is particularly used in low-melting alloys.
It has a high boiling point, which makes it ideal for recording temperatures that would vaporise a thermometer.
Biological role
Gallium has no known biological role. It is non-toxic.
Natural abundance
It is present in trace amounts in the minerals diaspore, sphalerite, germanite, bauxite and coal. It is mainly produced as a by-product of zinc refining.
The metal can be obtained by electrolysis of a solution of gallium(III) hydroxide in potassium hydroxide.
Gallium was discovered in Paris by Paul-Émile Lecoq de Boisbaudran in 1875. He observed a new violet line in the atomic spectrum of some zinc he had extracted from a sample of zinc blende ore (ZnS) from the Pyrenees. He knew it meant that an unknown element was present.
What Boisbaudran didn’t realise was that its existence, and properties, had been predicted by Mendeleev whose periodic table showed there was a gap below aluminium which was yet to be occupied. He forecast that the missing element’s atomic weight would be around 68 and its density would be 5.9 g/cm3.
By November of 1875, Boisbaudran had isolated and purified the new metal and shown that it was like aluminium. In December 1875 he announced it to the French Academy of Sciences.
| Atomic radius, non-bonded (Å) | 1.87 | Covalent radius (Å) | 1.23 |
| Electron affinity (kJ mol−1) | 41.49 |
Electronegativity (Pauling scale) |
1.81 |
|
Ionisation energies (kJ mol−1) |
1st
578.845
2nd
1979.411
3rd
2964.589
4th
6101.829
5th
8298.7
6th
10873.9
7th
13594.8
8th
16392.9
|
||
| Common oxidation states | 3 | ||||
| Isotopes | Isotope | Atomic mass | Natural abundance (%) | Half life | Mode of decay |
| 69Ga | 68.926 | 60.108 | - | - | |
| 71Ga | 70.925 | 39.892 | > 2.4 x 1026 y | β- | |
|
|
|
Specific heat capacity (J kg−1 K−1) |
373 | Young's modulus (GPa) | Unknown | |||||||||||
| Shear modulus (GPa) | Unknown | Bulk modulus (GPa) | Unknown | |||||||||||
| Vapour pressure | ||||||||||||||
| Temperature (K) |
|
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| Pressure (Pa) |
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| Listen to Gallium Podcast |
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Transcript :
Chemistry in its element: gallium(Promo) You're listening to Chemistry in its element brought to you by Chemistry World, the magazine of the Royal Society of Chemistry. (End promo) Chris Smith Hello and this week to the story of the element that's named after a rooster although the man here to tell us about it actually chickened out when it came to eating some of this chemical, although he did confess to giving it a quick lick. And to tell us how it tasted and why Gallium could hold the key to the next generation of LEDs, here's Andrea Sella. Andrea Sella When I was a child growing up in New York, some of the sweets most sort after by my classmates and me, with yellow and brown packs of highly coloured sugar coated chocolate pills bearing the characters M & M. You could pop them into your mouth one by one and suck them gently until the smooth surface became crumbling to reveal the smooth milk chocolate beneath; alternatively you cold cram your mouth with as many as you could and crunch them greedily to cause an explosion of sound, texture and flavour in your head. A secret pleasure that was hard to beat. I was reminded of all this when a colleague of mine who was having a lab clear out, knocked on my door and asked me knowing full well what my answer would be, 'Hi Andrea, would you like a lump of Gallium?', 'of course I would love some Gallium', I gurgled. The M & M of the elements; the one which reputedly melts in your mouth but not in your hand, he handed me a small plastic bag badly stained with black smudges. I undid the knot eagerly and there it was, a gleaming silvery lump bearing all the hallmarks of a metal that had been repeatedly melted and then refrozen. Gallium, you see, melts at 30oC, which means that on a hot day, you hold it in your pocket at your peril. Surprisingly however it's not very volatile. In fact Gallium has the largest liquid range of any material known to man. Its boiling point is just over 2400oC. So unlike other liquid metals, there is no toxic vapour to worry about. Bizarrely as well, the metal contracts as it melts, rather like water. So solid Gallium floats on its liquid, a property shared only by a couple of other elements, Bismuth and Antimony. The reason for this weird melting behaviour has been a matter of argument and speculation for about 50 years. It's now fairly well established that Gallium surrounds itself with more of its neighbours when in the liquid than in the solid, although the reasons for this still remains obscure. Yet for all its strangeness the discovery of this odd element was no accident. Dmitri Mendeleev, the bearded Russian chemist who constructed the periodic table as we know it today, spotted a number of gaps and discrepancies in his arrangement. One of these was the absence of an element which he expected to fit below Aluminum. So confident was he in the correctness of his framework that he named the as yet undiscovered element ekaaluminium. Six years later in 1875, an ambitious French element hunter François Lecoq de Boisbaudran one of the earliest proponents of the new-fangled technique of spectroscopy spotted a line in the violet part of the visible spectrum at 417nm in a sample of zinc sulphide, he realized that this must come from a new element. Working in his home laboratory in spite of starting from some 52 kilos of an ore from the Pyrenees, it took three weeks for him to accumulate a couple of milligrams of the mysterious material. He then scaled up his extraction and took the product of his labours to Paris where he studied it further in Adolphe Wurtz's lab. Just before Christmas in 1875, Lecoq presented his results to the French academy proudly displaying a sample of almost 600mg, less than a gram of material harvested from 450 kilos of ore. And the name Lecoq patriotically chose to base it on the Latin name for France, Gallia; Gaul in English. But it was immediately pointed out that there might be something more to the name than met the eye. The Latin word for a rooster is Gallus, Lecoq, rooster, Gallium, get it. It seems he may have been a rather cunning linguist as well as a chemist. Either way, Lecoq could look back with some satisfaction at having helped to cement Mendeleev's table, was the foundation stone of chemistry. He then moved on to the intriguing mystery of the 'rare earths', ultimately isolating two more elements and conforming the existence of several more. Gallium soon moved into the main stream of chemistry. Nowadays the metal itself finds few uses, but its compound with arsenic, gallium arsenide has for several years been touted as a possible replacement for Silicon. Since not only is it a semiconductor but it is one with a direct band gap, in other words it can be made to emit light, a property which is particularly useful for infrared but also visible LEDs. Gallium arsenide solar cells are also much more efficient than those made of conventional Silicon and are being used in solar powered cars and in space probes. But I'm sure you really want to know is, if this really is the M & M element, what does it taste like? I knew you would ask. So I had a quick lick a couple of days back and the answer is it doesn't actually taste very much to be honest. There's a faintly astringent, metallic taste which lingers on your tongue for few hours. And when it is molten, sorry I'll leave that experiment for someone more intrepid than I. Chris Smith UCL chemist Andrea Sella with the story of gallium, the element that Lecoq allegedly named after himself. Next week we are meeting the metal that powers nuclear rectors but can also be lethal for another reason. Polly Arnold Because it is so dense DU is also used in shielding in the keels of boats and more controversially in the noses of armour piercing weapons. The metal has the desirable ability to self sharpen as it pierces a target rather than mushrooming upon impact, the way conventional tungsten carbide tipped weapons do. Chris Smith DU being Depleted Uranium of course and Edinburgh chemist Polly Arnold will be here to tell us its story as well as revealing why it actually makes very beautiful glass on next week's Chemistry in its element. I hope you can join us. I'm Chris Smith, thank you for listening and good bye. (Promo) Chemistry in its element is brought to you by the Royal Society of Chemistry and produced by thenakedscientists.com. There's more information and other episodes of Chemistry in its element on our website at chemistryworld.org/elements. (End promo)
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Visual Elements images and videos
© Murray Robertson 1998-2017.
W. M. Haynes, ed., CRC Handbook of Chemistry and Physics, CRC Press/Taylor and Francis, Boca Raton, FL, 95th Edition, Internet Version 2015, accessed December 2014.
Tables of Physical & Chemical Constants, Kaye & Laby Online, 16th edition, 1995. Version 1.0 (2005), accessed December 2014.
J. S. Coursey, D. J. Schwab, J. J. Tsai, and R. A. Dragoset, Atomic Weights and Isotopic Compositions (version 4.1), 2015, National Institute of Standards and Technology, Gaithersburg, MD, accessed November 2016.
T. L. Cottrell, The Strengths of Chemical Bonds, Butterworth, London, 1954.
John Emsley, Nature’s Building Blocks: An A-Z Guide to the Elements, Oxford University Press, New York, 2nd Edition, 2011.
Thomas Jefferson National Accelerator Facility - Office of Science Education, It’s Elemental - The Periodic Table of Elements, accessed December 2014.
Periodic Table of Videos, accessed December 2014.
Derived in part from material provided by the British Geological Survey © NERC.
Elements 1-112, 114, 116 and 117 © John Emsley 2012. Elements 113, 115, 117 and 118 © Royal Society of Chemistry 2017.
Produced by The Naked Scientists.
Created by video journalist Brady Haran working with chemists at The University of Nottingham.
© Murray Robertson 1998-2017.
Data
W. M. Haynes, ed., CRC Handbook of Chemistry and Physics, CRC Press/Taylor and Francis, Boca Raton, FL, 95th Edition, Internet Version 2015, accessed December 2014.
Tables of Physical & Chemical Constants, Kaye & Laby Online, 16th edition, 1995. Version 1.0 (2005), accessed December 2014.
J. S. Coursey, D. J. Schwab, J. J. Tsai, and R. A. Dragoset, Atomic Weights and Isotopic Compositions (version 4.1), 2015, National Institute of Standards and Technology, Gaithersburg, MD, accessed November 2016.
T. L. Cottrell, The Strengths of Chemical Bonds, Butterworth, London, 1954.
Uses and properties
John Emsley, Nature’s Building Blocks: An A-Z Guide to the Elements, Oxford University Press, New York, 2nd Edition, 2011.
Thomas Jefferson National Accelerator Facility - Office of Science Education, It’s Elemental - The Periodic Table of Elements, accessed December 2014.
Periodic Table of Videos, accessed December 2014.
Supply risk data
Derived in part from material provided by the British Geological Survey © NERC.
History text
Elements 1-112, 114, 116 and 117 © John Emsley 2012. Elements 113, 115, 117 and 118 © Royal Society of Chemistry 2017.
Podcasts
Produced by The Naked Scientists.
Periodic Table of Videos
Created by video journalist Brady Haran working with chemists at The University of Nottingham.
