Alkali Metals Essay, Research Paper

The six chemical elements that are known as alkali metals are lithium (Li), sodium

(Na), potassium (K), rubidium (Rb), cesium (Cs), and the extremely rare radioactive

substance called francium (Fr). Cesium and Francium are the most reactive elements in

this group. The word alkali comes from the Arabic word al-qili, meaning plant ashes.

Plant

ashes were the first source of alkali metal compounds. The alkali metals occupy the first

column of the periodic table of the elements. Since these metals are all in the same group

on the periodic table of the elements they all have similar qualities. They all have a nS1

electron configuration. They do not occur freely in nature. They are softer than other

metals, and have lower melting points and densities. They are all silver-white in color,

they

are all malleable, ductile, and very good at conducting heat and electricity. All of the

alkali

metals have one electron in their outer most energy level so they all bond easily. All of the

alkali metals also react violently with water. In the laboratory pure alkali metals are

generally stored in oil to prevent them from forming compounds with other elements. The

oil also prevents water vapor in the air from reaching the metals. Compounds of alkali

metals rank among the most common and most useful of all chemicals. Millions of tons of

alkali metal salts are used by industry each year. The salts come from mines and wells.

Sodium and potassium salts are raw materials for sodium hydroxide and potassium

hydroxide. These alkali metal compounds and others made from them are used in making

glass, paper, soap, and textiles; in refining petroleum; and in preparing leather.

Lithium is the lightest of the solid elements, this soft, white metal is found in minerals

such

as petalite and spodumene. The word Lithium comes from the Greek word ?lithos?

meaning ?stone?. Large deposits are found in North Carolina, Nevada, and California. It

imparts a crimson color to flame and floats on water. Chemically active, its compounds

have many uses, including lithium carbonate in treating manic-depressive psychosis. Other

compounds are used as thickeners in lubricating greases, as brines for refrigerating and

air-conditioning systems, and in dry cells and storage batteries. It was discovered in 1817

by Johan August Arfwedson. Lithium is a low density solid only about half as dense as

water. A freshly cut lithium chunk is silvery but it tarnishes in a minute or so in air to give

a

gray surface.

Life could not exist without compounds of sodium. These compounds hold water in body

tissues, and a severe deficiency of sodium can cause death. Blood contains sodium

compounds in solution. Sodium compounds are used in industry in the manufacture of

chemicals and pharmaceuticals, in metallurgy, in sodium vapor lamps, and in the

production of hundreds of everyday products. One of the most common sodium

compounds is table salt, or sodium chloride (NaCl). In its pure form sodium is a

silver-white, soft and waxy metallic element. Another important compound is sodium

bicarbonate, or baking soda. It is the sixth most abundant element on Earth and occurs in

more than trace amounts in the stars and sun. Pure sodium is used in the manufacture of

tetraethyl lead and as a cooling agent in nuclear reactors. Sodium hydroxide is used in the

manufacture of soap, rayon, and paper; in oil refining; and in the textile and rubber

industries.

Potassium is the seventh most abundant element in the Earth’s crust, potassium occurs in

many silicate rocks and minerals. The major commercial source is salt deposits, but a

small

fraction is obtained from plant and animal sources. Water-soluble potassium compounds

are economically recovered. They are frequently found as dry mineral deposits and as

brines. Most potassium is present in insoluble minerals, making it difficult to obtain, but it

can be prepared commercially by electrolysis from some refinable minerals. Potassium

compounds are used in fertilizers, soaps, explosives, glass, baking powder, tanning, and

water purification. It exists as three natural isotopes, with atomic mass numbers 39, 40,

and 41. Potassium-40 is radioactive. The most abundant isotope is potassium-39.

Rubidium is the second most reactive metal, this element is very soft and silvery-white

and

was named for the two red lines of its spectrum. Found in the minerals lepidolite,

pollucite,

and others, it is used in photoelectric cells and as a “getter” in electron tubes to scavenge

for traces of unwanted gases. It is a widely distributed element that occurs in small

amounts

in many minerals and in certain mineral waters. It is also found in small quantities in tea,

coffee, tobacco, and other plants. It was discovered in 1861 by Robert Bunsen and Gustav

Kirchhoff.

Cesium is a silvery-white alkali metal used in television cameras, atomic clocks, and as a

“getter” in electron tubes to clear out traces of unwanted oxygen in the sealed tube. One of

only three metals that are liquid at room temperature, cesium occurs in the minerals

pollucite and lepidolite in the Earth’s crust. It was the first element to be discovered

spectroscopically. Because it emits electrons when exposed to light, cesium is used in

photoelectric cells. The radioactive isotope cesium-137, which is produced by nuclear

fission, emits more energy than radium and is used in medical and industrial research as an

isotopic tracer. Commercial cesium usually contains rubidium, with which it usually

occurs

in minerals and which resembles it so closely that no effort is made to separate them.

Robert Bunsen and Gustav Kirchhoff discovered it in 1860 and named it for the unique

blue lines of its spectrum.

Francium is the heaviest member of alkali metals group in periodic table. Found in

uranium minerals, even though there is less than 1 ounce of francium in the Earth’s crust at

any one time. It can be made artificially by bombarding thorium with protons. There are

20

known isotopes. Its isotopes range in atomic weight from 204 to 224. Francium is

produced when the radioactive element actinium disintegrates. The longest-lived isotope,

francium-223, oractinium-K, has a half-life of 22 minutes. It was discovered in 1939 by

Marguerite Perey of the Curie Institute.