(a 2s electron). In fact, for the alkali metals (Group 1) the ease of giving upan electron varies as follows:

Loses anelectron

most easily

Note that as we go down the group, the metals become more likely to losean electron. This makes sense because as we go down the group, the electronbeing removed resides, on average, farther and farther from the nucleus.That is, the 6s electron lost from Cs is much farther from the attractive pos-itive nucleus—and so is easier to remove—than the 2s electron that mustbe removed from a lithium atom.

Cs 7 Rb 7 K 7 Na 7 Li

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C H E M I S T R Y I N F O C U S

Fireworks

The art of using mixtures of chemicals to produceexplosives is an ancient one. Black powder—a mix-ture of potassium nitrate, charcoal, and sulfur—was being used in China well before A.D. 1000, andit has been used through the centuries in militaryexplosives, in construction blasting, and for fire-works.

Before the nineteenth century, fireworks wereconfined mainly to rockets and loud bangs. Orangeand yellow colors came from the presence of char-coal and iron filings. However, with the greatadvances in chemistry in the nineteenth century,new compounds found their way into fireworks.Salts of copper, strontium, and barium added bril-liant colors. Magnesium and aluminum metals gavea dazzling white light.

How do fireworks produce their brilliant colorsand loud bangs? Actually, only a handful of differ-ent chemicals are responsible for most of the spec-tacular effects. To produce the noise and flashes,an oxidizer (something with a strong affinity forelectrons) is reacted with a metal such as magne-sium or aluminum mixed with sulfur. The resultingreaction produces a brilliant flash, which is due tothe aluminum or magnesium burning, and a loudreport is produced by the rapidly expanding gases.For a color effect, an element with a colored flameis included.

Yellow colors in fireworks are due to sodium.Strontium salts give the red color familiar fromhighway safety flares. Barium salts give a greencolor.

Although you might think that the chemistry offireworks is simple, achieving the vivid white flash-

es and the brilliant colors requires complex combi-nations of chemicals. For example, because thewhite flashes produce high flame temperatures,the colors tend to wash out. Another problem aris-es from the use of sodium salts. Because sodiumproduces an extremely bright yellow color, sodiumsalts cannot be used when other colors are desired.In short, the manufacture of fireworks that producethe desired effects and are also safe to handlerequires very careful selection of chemicals.*

These brightly colored fireworks are the result ofcomplex mixtures of chemicals.

*The chemical mixtures in fireworks are very dangerous. Do notexperiment with chemicals on your own.

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