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Chalcogens (Group 6A Elements): Definition & Properties

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  • 0:02 Chalcogens
  • 1:14 Properties the…
  • 3:09 Individual Elements…
  • 6:50 Lesson Summary
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Lesson Transcript
Instructor: Julie Zundel

Julie has taught high school Zoology, Biology, Physical Science and Chem Tech. She has a Bachelor of Science in Biology and a Master of Education.

Some can kill you, some are useful, and one is vital to your survival. Welcome to the chalcogens! This lesson will list common properties, and will then share some uses and characteristics of these diverse Group 6A elements.

Chalcogens

Although what I am about to tell you sounds like a story out of a movie, it really happened. In November 2006, a former KGB agent named Alexander Litvinenko became extremely sick after drinking tea with a former Russian agent. His hair fell out, the number of blood cells in his body declined, he had gastrointestinal problems such as nausea and vomiting, and then he eventually died. It was later determined he was poisoned by a Group 6A element called polonium (but more on Litvinenko later).

Polonium is one of five elements that belong to the chalcogens, or Group 6A elements, which include oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and polonium (Po). Depending on where you're looking, this group can also be called Group 16 or Group VIA - all mean the same thing.

Elements are placed in groups, or the vertical columns on a periodic table, because they share certain properties. You may have noticed that oxygen is in the same group as polonium, and it would appear that a radioactive element that killed a former KGB agent would have very little in common with the air that keeps you alive, but they actually have a quite a few things in common.

Properties the Chalcogens Share

So, what do polonium and oxygen have in common? Oxygen, polonium, and the rest of the chalcogens all have six valence electrons; these are the outermost electrons, farthest away from the center of the atom. They give elements certain properties and help determine who the element can bond (or attach) with.

Most members of this group gain two electrons from another element so they can have eight valence electrons. Atoms are stable when they have eight valence electrons, so by gaining two, the chalcogens become stable. Electrons have a negative charge, and because most of the chalcogens gain two electrons, they get a -2 charge. This can also be referred to as a -2 oxidation state. An atom with a negative charge is called an anion.

So, the -2 oxidation state is the most common, but some of the other chalcogens can have other oxidation states. Sulfur, for example, can have oxidation states of +4 and +6. This means that sulfur can lose electrons and become more positive. Atoms that have a positive charge are called cations. And just to confuse you more, selenium, tellurium, and polonium can have oxidation states of +6! Because oxidation states can vary, just remember that -2 is the most common oxidation state for the chalcogens!

As you go down the group, the elements become more metallic. Oxygen and sulfur are nonmetals, selenium can be classified as a nonmetal or a metalloid, tellurium is a metalloid, and polonium is a metal. Nonmetals, metalloids, and metals all have different properties. For example, metals are good conductors of heat and electricity and are malleable (or bendy), whereas nonmetals tend to be poor conductors and are brittle. Metalloids have properties of metals and nonmetals.

Individual Elements Within the Chalcogens

Take a deep breath! That was a lot of information! And as you take a deep breath, imagine oxygen entering your mouth, traveling to your lungs, and then diffusing into your bloodstream, nourishing your cells, which leads us to our first chalcogen: oxygen. Not only is oxygen vital to your survival, but oxygen is everywhere! By mass, it makes up almost half of the Earth's crust and 90% of water. It makes up almost 21% of the Earth's atmosphere and it is the third most abundant element in the universe! But there's more! Almost 67% of your mass is oxygen. Wow!

So now we know oxygen is everywhere and is pretty important for your survival, but what else is there to know about this element? Well, you probably know that it is a colorless gas at room temperature and it is tasteless and odorless, but did you know that it is used in the refining of petroleum products, in steel and iron manufacturing, and as an ingredient in rocket fuel?

Another element you might already be familiar with from the chalcogens is sulfur. Have you ever been to a hot springs and noticed an unpleasant odor? You can thank sulfur for that! At room temperature, sulfur is a brittle, yellow solid that is odorless and tasteless, but when you combine it with hydrogen and form hydrogen sulfide you get that rotten-egg smell you may have smelled at a hot spring.

Sulfur's biggest commercial use is for sulfuric acid, or sulfur that is bonded to hydrogen and oxygen atoms. Sulfuric acid is used in batteries, fertilizer, and in gunpowder, and can be quite dangerous. Exposure to your eyes can result in blindness, inhaling it can kill you, and if you get it on your skin, it can cause severe burns.

Selenium and tellurium are the lesser-known chalcogens. Like oxygen and sulfur, selenium can be classified as a nonmetal, but to make things a little confusing, it is sometimes classified as a metalloid, like tellurium. It can be found as two colors: red and grey, and it is used as an additive to glass, as a pigment in ceramics, and in some dandruff shampoos (talk about the wide range of uses!). And here's a fun fact: selenium is named after the Greek goddess of the moon, Selene (but more on that shortly).

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