Periodic Table: Elemental Forms - Video Tutorials & Practice Problems
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The elements of the Periodic Table exist in different elemental forms in the natural world
Elemental Forms
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Periodic Table: Elemental Forms
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Now the elements of the periodic table can exist in different forms in the natural world. Here, we can say that elements exist in their most stable state when they are monoatomic elements, diatomic elements, or polyatomic elements. When we say the term monoatomic elements, these are the elements that are stable alone when found in nature because mono means 1. So if we take a look here at the periodic table, lithium, we could say magnesium, we could say zinc. None of them are shaded red or blue, so they all exist in their most stable state as monoatomic elements. So you'd find Lithium by itself, Magnesium by itself, Zinc by itself. Other elements on the periodic table are most stable and found in a diatomic structure. So these diatomic elements, these are the elements that are stable as pairs when found in nature because di means 2. To help us remember the diatomic elements, just remember have no fear of ice cold beer. So here this would be h2, n 2f2o2. I is I 2. Now this c here is not carbon, it's chlorine, so that's cl2, and b here is not boron, but bromine, so this is br 2. So these are your diatomic elements of the periodic table. So hydrogen exists as a diatomic, nitrogen, oxygen, fluorine, chlorine, bromine, and iodine. Now finally, some elements in their most stable state in nature, they exist as polyatomic elements. These are elements that are stable in numbers greater than 2 because poly means many. On our periodic table, we see that our polyatomic elements are phosphorus, sulfur, and selenium. Phosphorus in nature exists as p4, Sulfur exists as s8. And remember, we said that elements in the same group or column tend to have similar chemical properties. Because sulfur is S8, selenium would also have 8 because they're in the same group. So selenium would be SE8. So these are the most natural forms of the elements when we look at them in nature. So just remember that we have monoatomic, diatomic, and polyatomic elements.
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Periodic Table: Elemental Forms Example 1
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So in this example question, it says, which of the following choices represents a monoatomic element that is also a chalcogen? Remember, some groups have unique names. A chalcogen is from group 6 a or what we know as group 16. So if we come up here, group 6a or group 16, which is the same thing, would be this column here. Oxygen, sulfur, and selenium are automatically out because none of them are monoatomic. The monoatomic elements from this group would be TE, PO, or LV. If we look, a couldn't be our answer because it's monoatomic, but it is not a chalpogen. Sulfur is a chalcogen because it's in that group 6 a, but it is polyatomic. T e is one of the 3 that we named, so it's our answer. Chlorine is not a chalcogen, it's in group 7 a, so it's a halogen. Also, it's diatomic. Then finally, lithium. Lithium is monoatomic, yes, but it is an alkali metal and not a chalcogen. It's in group 1 a. So out of all our choices, only option c is the correct answer here.
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Periodic Table: Elemental Forms
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Sometimes we can refer to multiple elements together as being either homonuclear or heteronuclear. In homonuclear compounds, these are compounds composed of identical elements. So this would represent our diatomic and polyatomic elements. So we talk about h2cl2p4s8. These would be our homonuclear elements or we can name them diatomic elements or polyatomic elements. In heteronuclear compounds, this is when our compounds are composed of different elements. So a good example would be water, which is H2O, carbon dioxide, which is c o two, ammonia gas, so ammonia is big with fertilizers, that's NH 3, also glucose, which we've talked about in the past, C6H1206. So just remember, elements can exist as either monoatomic, diatomic, or polyatomic elements, and then we can also refer to them as either homonuclear if all the elements are the same, or heteronuclear, if the elements together are different.
Homonuclear:composed of identical elements. Heteronuclear:composed of different elements.
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Problem
Problem
Which of the following is a homonuclear polyatomic element?
A
Chlorine
B
Oxygen
C
Hydrogen
D
Iron
E
Selenium
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