August 27 – Discovery of Gallium!!

Gallium doesn’t exist by itself in nature, so it took some doing to find it!

Dmitri Mendeleev predicted its existence, using the periodic table of elements: There was zinc (Zn) with atomic number 30, and arsenic (As) with atomic number 33… So, Mendeleev asked, where were the elements with the atomic numbers 31 and 32?

The beauty of Mendeleev’s periodic table is that elements share properties with the elements positioned above them on the table. So Mendeleev was able to guess some of the properties of the elements before they had even been discovered.

After 15 years of work, on this date in 1875, Paul Emile Lecoq de Boisaudran discovered the predicted element with atomic number 31. He named the new element gallium in honor of his country, France (Gallia).

Gallium is right under aluminum on the periodic table, and like aluminum it is a soft, silvery metal.

Lecoq made his discovery with a spectroscope, which uses a prism to separate the various colors of light from a light source. When chemists use spectroscopes, they either burn a bit of material and analyze the light emitted from the burning material, or they create a gas form of the material and shine white light through the gas and see which light is absorbed.

In this case, Lecoq was analyzing zinc blende, and he found two violet lines that were not accounted for by other elements in the ore. Later the same year, Lecoq was able to isolate gallium using a process called electrolysis.

Gallium has a very low melting point. Like, if you try to hold it in your hand, it melts!

Create a spectrum.

In other words, make a rainbow! 

Use a glass prism to separate white light into a rainbow. Yep, a rainbow is a spectrum! Remember, each raindrop acts as a prism separating the light.

If you don’t have a prism, check out this YouTube video of a prism creating a rainbow.

Or make a rainbow in some other way – there are lots!

To make a rainbow with a hose, make sure the sun isn’t overhead and stand so that the sun is at your back. Then shoot the hose toward your shadow – making sure that your thumb or a nozzle makes the stream of water into a spray of many drops of water.

A glass of water can make a rainbow!

CDs can make rainbows!

Here is a video about a man called the Rainbow Maker.