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All 118 elements

Element 5 ·metalloid

péng — "boron"

Boron

How the character is built

The radical marks this as a solid non-metal, and that is not a coincidence of this one character — it holds right across the table. Read the radical first and the element's state at room temperature is already settled.

Where you actually meet it

硼砂 (péngshā) borax

The element itself

Boron concentrates in a very specific kind of place: a closed desert basin fed by volcanic hot springs, where borate-rich water evaporates and crystallises. There are only a handful of such basins on Earth, which is why the world's borax comes overwhelmingly from western Turkey and the Mojave Desert of California. In the 1880s the Mojave product was hauled out by wagon trains pulled by twenty mules at a stretch, an image that outlived the industry that produced it. Boron also makes glass tough against thermal shock, which is why laboratory glassware and oven dishes are borosilicate.

Where it sits among the 118

Boron melts at 2076°C (2349 K) — lower than 10 of the 97 elements whose melting point has been measured, and higher than 86. The grey dots are the rest of the table.
In the Earth's crust there is about 10 grams in every tonne of rock. That makes it commoner than 56 of the 93 elements that occur naturally at all. The scale is logarithmic: each gridline is ten times the one below it.

First isolated in 1808.

In living things

Boron is essential to plants and to almost nothing else. It works as a crosslinker in the cell wall: a borate ion bridges two chains of a pectin called rhamnogalacturonan-II, forming a diester that ties the wall network together, and without it growing tips and root apices simply fail to hold their structure. Boron is one of the more mobile nutrients in soil, easily leached from sandy ground in wet climates and easily accumulated to excess in dry, irrigated ones, which makes it a recurring headache in agriculture — a nutrient whose useful range is unusually narrow.

Where it comes from in China

Boron runs two ways in China. The salt lakes of the Tibetan plateau have yielded borax for centuries, and it travelled west across the mountains as a trade good long before anyone knew it contained an element — medieval European craftsmen knew it as tincal and used it as a flux for soldering. The industrial source today is far less romantic and much larger: magnesium-borate rock in the old crystalline basement of eastern Liaoning.

Liaoning 辽宁Tibet 西藏
Tibet and Liaoning — shaded on a map drawn from Natural Earth's public-domain data.

The full entry

For stroke order, example sentences, audio and the complete set of meanings, see the dictionary entry.

Boron in the dictionary →

Others built the same way

Every one of these carries , and every one is a solid non-metal.

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