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150 Years of Predicting the Elements of Electronics

https://blog.screamingcircuits.com/2019/02/150-years-of-predicting-the-elements-of-electronics.html

A poster of this was likely tacked to the wall of every science classroom you sat in and -- if you’re anything like me -- you may still have occasional nightmares about having to memorize the positions. What is it?

That’s right: the periodic table of the elements, which celebrates its 150th birthday this year. And, speaking of nightmares, the inventor of the table, Dmitri Mendeleev, claimed the complete arrangement of the elements came to him in a dream! Similarly, the idea to write a few blog posts about the periodic table and its importance to electrical engineering came to our usual blog author in a dream, so here we are. Well, here I am. He slept late and asked me to write about it.

If you remember your science lessons, you might recall that Mendeleev was not the first chemist to propose a periodic table; even Plato -- who coined the term “elements” -- had vague notions about how they could be ordered. But Mendeleev’s proposed design, presented to the Russian Chemical Society in 1869, stood out from all the others in three important ways: first, he ordered the elements according to their atomic weight and found that elements with similar weights have similar chemical properties. Second, his table provided for variance from atomic weight order. Third, and most impressive: Mendeleev’s arrangement correctly predicted elements not yet discovered -- he even left spaces for them!

Some dismissed Mendeleev for his claim he could predict more elements -- other chemists with their own tables had tried to do so and failed. But just six years later, he was proven to be correct when gallium (Ga) was discovered, as he had proposed, with a spectroscope. It fit perfectly into the space he had left open for it on his table.

Mendeleev had called gallium “eka-aluminum” as he predicted -- correctly -- that the element would sit below aluminum on his table. He had made several other predictions about its properties, most of which were correct. In fact, his prediction of gallium’s atomic weight was only off by 1.723 (about 2.5%).

The discovery of gallium was critical to Mendeleev’s table being accepted and brought to a wider world. His method of classifying, ordering, and predicting elements became the foundation for modern chemical discoveries.

It is especially interesting for us, as electrical engineers, that gallium was the element to save Mendeleev’s reputation: the element was not considered particularly useful until the age of semiconductors. Yes, gallium is predominantly used in electronics!

You may know it in the form of gallium arsenide, used in high-speed, severe environment electronics. If you’ve ever worked with microwave circuits, high-speed switching circuits, or infrared circuits, you’ve used it. It is also used to produce solid-state items like transistors and blue and violet light-emitting diodes.

Gallium is a powerful little element, and one that is being used more and more, especially as 4G smartphones use 10 times more GaAs than older models, and 5G will certainly demand even more. And so, as we celebrate the periodic table this year, we not only owe Mendeleev our thanks, but also share with him a deep appreciation for the element that solidified his table in science for perpetuity: the mighty gallium.

Technical FocusSara Shepherd