Barium
Barium's history is quite interesting and this is how it went. The first time this element was ever seen was in the Middle Ages. Originally called scherspat the element was mysterious to these people who had only seen it in ore form. Later on it was found to have a special quality that made it glow in dark after it was left in sunlight for awhile. It was given brief fame by Vincenzo Casciarola 1600. In 1788 a man named Lavsier guessed that barium was a compound that consisted of a nonmetal and an unknown. This turned out to be wrong. In the Scheele investigation indicated that the compounds he obtained differed from any known compound but didn't know what to do. Then in 1808 Sir Humphry Davy discovered it first in pure form. He renamed barium after the Greek word barytes meaning heavy. After that people tried to change the name to plutonium but did not succeed. And that brings us to now.
Barium has the symbol Ba and the atomic number of 56.(see ex. 2) It has a mass of 137.34 and a density of 175 g/cm3 at 20 degrees Celsius. It's melting point is 725 degrees Celsius and it's boiling point is 1640 degrees Celsius. It is silver in color. Barium is the 5th alkaline Earth metal forming group II of the periodic table. It is electropositive and very reactive. It tendency to absorb and combine with oxygen and nitrogen. Barium hydrogen is a soluble in water and is a strong base. Barium oxide is used as a laboratory source of small amounts of peroxide. The oxidation of barium oxide in air produces barium peroxide, which, reacting with diluted sulfuric acid, yeilds hydrogen peroxide.
Barium ion is double positive and used to precipitate larger anions. Some compounds we find from barium are as follows: barium sulfate, barium carbonate, barium nitrate, barium hydrate. Barium has many uses in everyday life. Bariumoxide is used to remove oxygen from vacuum tubes. Barium carbonate is used in many things such optical, permanent magnets in loudspeaker, and rat poison. Barium nitrate is used in fireworks to make green. On an serious note, barium sulfate is to take X-rays which is called barium enema. People who do this must swallow insoluble barium and then get X-rayed.
The periodic table is a classification and tabulation of the chemical elements in order of their atomic numbers.( see ex. 1)The table was first made in the 19th century. A element is represent on the chart by it's atomic number, weight, symbol, and name.( see ex. 2) In each column of the table there are elements all having similar properties. The lightest is on thetop and the heaviest is on the bottom. They are also classified in groups: metals, nonmetal, metalloids, etc. There are 120 elements in all in which 20 are man-made and 90 are natural.