31GaGallium69.723

A real sample of the element Gallium — Real sample photo

Gallium (Ga)

“The metal that melts in a warm fist at 29.8 °C — and that lights up phone screens as brilliant GaN LEDs.”

View group 13 →View period 4 →See in trends →

Atomic number31

Atomic mass69.723

Group13

Period4

BlockP-block

PhaseSolid

Electron structure

How its electrons are arranged

[Ar] 3d¹⁰ 4s² 4p¹

Shell 1

2e⁻

Shell 2

8e⁻

Shell 3

18e⁻

Shell 4

3e⁻

Computed from the aufbau principle, with known real-world exceptions applied automatically.

🎯 Exam focus

Questions to practise

Try each question yourself first — then open it to read the full model answer.

1How did gallium’s discovery in 1875 vindicate Mendeleev’s periodic table, and which two properties had he predicted in advance?

Model answerIn 1871 Mendeleev left a blank labelled eka-aluminium and predicted the missing element’s atomic mass and its density — about 5.9. When Lecoq de Boisbaudran discovered the metal in 1875 and first measured a density of 4.7, Mendeleev wrote insisting he re-measure; the corrected value came out at 5.9, matching the forecast exactly. So exact a match could not be luck, and the periodic table became famous overnight.

2Name the gallium compound that makes the blue LEDs in phone screens possible, and name the prize its inventors won in 2014.

Model answerThe compound is gallium nitride, GaN — the semiconductor that finally tamed efficient blue light. Its inventors, Isamu Akasaki, Hiroshi Amano and Shuji Nakamura, shared the 2014 Nobel Prize in Chemistry for the efficient blue LED; blue light plus a phosphor gave white LEDs, the bright low-power glow now behind every phone screen and bulb.

3Why would a gallium spoon melt away in a cup of hot milk-tea, while a steel spoon obviously survives?

Model answerEverything rests on melting point. Gallium melts at just 29.8 °C, while hot milk-tea is served around 60–70 °C, far above that mark, so the cup’s heat alone liquefies the spoon into a shining puddle. Steel is iron-based and does not melt until about 1,400 °C, so a teacup’s warmth leaves it completely untouched.

4Gallium melts at 29.8 °C yet boils only near 2400 °C. Why does this enormous liquid range make it a useful thermometer metal?

Model answerA thermometer metal must stay liquid across the whole scale it reads, and gallium’s liquid range — 29.8 °C to nearly 2400 °C — is among the widest of any element, so ordinary use never boils it away. In practice gallium is alloyed with indium and tin into Galinstan, which drops the freezing point below zero while keeping the wide range; the silvery, non-toxic liquid thus replaces banned mercury in hospital thermometers.

5Write gallium’s electron configuration and state its group, period and block. How many valence electrons does it have?

Model answerGallium is [Ar] 3d¹⁰ 4s² 4p¹. The highest occupied shell is n = 4, so Period 4; the differentiating electron enters a 4p orbital, so p-block; and the 4s² 4p¹ outer shell carries three valence electrons, fixing Group 13 (10 + 3) beside boron and aluminium. Losing all three gives the Ga³⁺ of its common compounds.

6What does the name “gallium” honour, and what was the teasing accusation that the discoverer had smuggled his own name into it?

Model answerThe name honours Gallia, Latin for France, the homeland of its discoverer Lecoq de Boisbaudran. The teasing accusation came from Latin gallus, “rooster”: in French that bird is coq, and the discoverer’s surname was Lecoq — so wags whispered that by naming the element after Gaul he had smuggled his own name into the periodic table as well.

Quick answers

One fact, one page

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Electron configurationThe full arrangement, step by step ValencyHow many bonds it forms Atomic massThe standard weight, explained Metal or nonmetalWhich family it belongs to Everyday usesWhere you meet it daily

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The notes

About the element

Characteristics

Melts at 29.8 °C — lower than a hot Dhaka afternoon — yet boils only near 2400 °C, one of the widest liquid ranges of any element.
Electron configuration [Ar] 3d¹⁰ 4s² 4p¹ — three valence electrons, so it shares Group 13 with boron and aluminium and usually forms Ga³⁺ compounds.
Combines with arsenic and nitrogen into GaAs and GaN — semiconductors that convert electricity straight into LED and laser light.
Like water, it expands slightly on freezing; liquid gallium also wets glass and leaves mirror-bright streaks wherever it flows.
A key ingredient of Galinstan (gallium-indium-tin alloy), the non-toxic liquid metal that replaces mercury in modern thermometers.

Appearance

A soft, silvery-blue metal that looks like a calm cousin of mercury yet is safe to touch. It melts at just 29.8 °C — the grip of a hand or a cup of hot tea will turn a spoon-shaped solid piece into a shining puddle.

Real world

Where you meet it

✦ Uses

Gallium nitride (GaN) blue and white LEDs — the invention behind the 2014 chemistry Nobel that lights phone screens, bulbs and billboards.
Gallium arsenide (GaAs) chips in smartphones and satellites — faster than silicon and doubling as the laser diodes that carry internet traffic through optical fibre.
Galinstan medical thermometers — mercury-free and safe, now standard in hospitals as mercury instruments are phased out.
Gallium-arsenide solar panels on satellites and space probes, which keep making power where ordinary silicon panels would fade.

◍ Everyday examples

The smartphone in your pocket hides a sprinkling of gallium in its screen’s LED backlight and its high-frequency signal chips.
On a 35 °C summer day in Bangladesh, a gallium spoon left outdoors would quietly melt into a shiny puddle.
Gallium never occurs free in nature — it hides in traces inside bauxite and zinc ores, so refineries rescue it as a by-product.

Story

History & name

In 1871 Mendeleev left a blank in his new periodic table for an undiscovered element he called eka-aluminium — boldly predicting its atomic mass, its density (about 5.9) and even its low melting point. In 1875 the French chemist Paul-Émile Lecoq de Boisbaudran found two unfamiliar violet lines in the spectrum of a zinc-blende ore from the Pyrenees and isolated the new metal by electrolysis. When Lecoq’s first density reading came out at 4.7, Mendeleev himself wrote insisting he re-measure; the corrected value, 5.9, matched the prediction and made the periodic table famous overnight. Lecoq named the element gallium after Gallia, Latin for his homeland, France.

Name originLatin Gallia, “France/Gaul”, the discoverer’s homeland — though gallus (“rooster”, coq in French) cheekily hinted at his own surname, Lecoq.

Neighbours

Nearby elements

The elements that sit right beside this one on the table — often the closest chemical cousins.

29CuCopper63.546 30ZnZinc65.38 32GeGermanium72.630 33AsArsenic74.922