Why is this element important in everyday life?
Selenium is very important to us in everyday life. It is used in photoelectric cells which are used in exposure meters for cameras and in light-sensitive switches. Selenium is also used in copy machines because its electrical conductivity increases in response to light shining on it. Selenium with its many compounds are used in metallugy, glass and ceramics, pigments, and medicines.
This leads us to another very important use of selenium. Selenium is an essential trace element for humans and animals. It is protective against cancer, heart disease, arthritis, and accelerated aging. It enters our bodies through our food, and to a lesser extent, water sources. The average intake of selenium from food ranges from 0.071 to 0.152 milligrams per person per day. This is enough to protect against diseases that may result from too little selenium.
Where is this element found in nature?
Selenium is not often found in its pure form but is usually combined with other substances. Most of the selenium in rocks is combined width sulfide minerals or with silver, copper, lead, and nickel minerals. When the rocks change to soils, the selenium combines with oxygen to form several substances. It may be obtained by heating or by evaporating carbon disulfide solutions above 75 degrees Celsius, or by cooling molten selenium.
What are the properties of the element?.
General Characteristics = The general characteristics of selenium is that it is a nonmetal but looks metallic. There are two crystalline modifications, one rhombic and one monoclinic. They are shaped in a hexagonal form. Selenium has several allotropes including red, gray, and black forms. Black Selenium is the type that is commercially available. Black Selenium's form is brittle but has a metallic luster. The other various forms of selenium range from metallic gray solid to one with a red glassy appearance. The most common selenium compounds are sodium selenite and sodium selenate. Some selenium compounds are gases but the most common forms are solid. Selenium is a moderately reactive substance. It burns in air, upon heating, to give dioxides.
Atomic Symbol = Se
Period Number = 4
Group Number and Family Name = Group 16, Oxygen Family
Atomic Number = 34
Atomic Mass = 78.96
Density = 4.82 g/cm3
Melting Point = 217 Degrees Celsius
Boiling Point = 685 Degrees Celsius
Electron Configuration =1s22s22p63s23p64s23d104p4
Shorthand Notation = [Ar]4s23d104p4
Common Reactions = Selenium combines directly with the halogens and with numerous metals and nonmetals. Selenium also reacts with many organic molecules.
Interesting Information = Selenium has a lot of major functions in our body. Some of these functions are: Selenium appears to improve the functioning of the immune system at its response to infections; it stimulates the formation and activity of natural killer cells, which destroy foreign bacteria and protein that enter the body; selenium helps to repair damage to DNA; and at high doses, selenium can decrease the rates of tumor cell growth.
Who is Senor Selenium?
"Thank you," replied Selenium. "This wonderful sunny day really helps to increase my conductivity."
Just as Selenium was finishing his job for Sulfur, Terrance Titanium walked in. The oxygen family was whispering, "Oh, look who just walked in. It's 'I think I'm so tough Titanium'," complained Odella Oxygen.
"Hmmm, excuse me, Senor Selenium. "Would you please copy my many uses for me so I can pass them around throughout the PT, Terrance Titanium asked?"
Selenium replied, "Maybe."
"Don't you maybe me, Selenium. "You listen to me. I could crush your hexagonal crystalline form before you could combine with the halogens to try to stop me," threatened Titanium!
Polonium stuck up for his fellow group member and said, "You'll have to get through me before you can get to Selenium." Titanium said nothing. Polonium added, "You must remember, Titanium, that Selenium is what protects your wonderful inventors, the humans, who use your many uses in their appliances. Without Selenium your humans would come down with cancer, heart disease, arthritis, and accelerated aging."
Titanium replied, "shut your pathetic, puny mouth Polonium. This is between me and Atomic Number 34." "As for you, you want to be like me but can't because you're a nonmetal. Are you going to copy these or not?"
Selenium replied, "Sure, I'd love to copy your wonderful uses for you." As Titanium placed the papers in Selenium, Selenium swallowed them up but didn't spit them back out!
"Where are my copies?" shouted Titanium!
"I don't know," said temperamental Selenium. "Maybe I wasn't purified enough from the copper or nickel minerals from which I come from," Selenium sarcastically stated. "Or maybe, I don't have enough light shining on me to form enough photoelectric cells to copy your so many uses!"
"Well, I'll just go find another form of Selenium, there's so many to choose from, like red, gray, and black forms. I don't need your fake metallic luster to copy me!" Titanium suddenly burst into tears! Odella Oxygen and Sam Sulfur were speechless.
Titanium blubbered, "You're so mean to me. All I tried to do was get some copies and you tore me down!"
Selenium sympathetically said, "Stop crying. We were just defending ourselves from your too tough self."
Titanium apologized and was about to leave. But before Titanium could wipe his eyes, Selenium snapped out his camera and shot a picture of Titanium, showing his one and only weak side, using his photoelectric cells for the exposure meters.
