In 1869, a Russian chemist Dmitri Mendeleev created the framework in which, stood all the known elements that we have, into a table known as the Periodic Table Of Elements.
They're basically a group of elements which are numbered or ordered according to the number of protons they have in their nucleus. And we all know, that Protons, Neutrons And Electrons are the constituents of An Atom. If you are curious to learn deep on atoms, then do visit my post:
Atoms: Electrons, Protons And Neutrons.
Well, it wasn't Mendeleev who discovered all the elements. Many scientists had discovered them. The fact is that, he left many gaps for the elements yet to be discovered (at his time) because now we have discovered all the 118 elements. Can there be more? If yes, then will another Mendeleev come to create more gaps? To be answered later in another post.
Today's discussion is on The Noble Gases. Please read my post on Atoms To have at least a knowledge of what stuff I am talking about right now.
Atoms: Electrons, Protons And Neutrons.
Today, we'll first look what are noble gases, then we will learn something about ALL the noble gases, so you'll have a complete grasp on it.
So, now having an idea about Atoms, let us get started.
First, Why are they even called "Noble Gases"? Are They honest or something. Let's answer that. Well, they're named Noble Gases because they are actually noble or have fine personality in terms of reactions. What does that mean? Basically, noble gases do not react with any other metal. Take Potassium for example, such a vigorous alkali metal. It reacts so vigorously with water that it is the most reactive metal in our periodic table! Then the reactivity series is followed by Sodium, Calcium etc.
So, back to noble gases. Noble gases are odorless, colorless and very low reactive gases.
Why are they low reactive!? It has an amazing reason! See, we all know atoms has electrons that revolves around the nucleus.
And if the valence electron is only 1 or 2 like lithium or potassium, then they are so much reactive. Why? I have already explained everything regarding valency in the Atoms post that I made. So, let me explain in short, it turns out the every element in our surrounding WANTS to be stable. Why? Simply to attain stability and not be SO MUCH reactive.
.gif)
And in order to be stable, their shell, according to quantum mechanics needs to be stable or completely filled. How can they become stable? Simply, by either of these methods -
1) Loosing An Electron. (More Precisely - Removing its Valence Shell electron)
2) Gaining An Electron. (More Precisely - Completing its Valence Shell)
3) Forming Ionic Bonds. (Giving the electron to another element atom)
4) Forming Covalent Bonds. (Sharing the electron shell with another element atom)
5) Forming Metallic Bonds. (A force that holds atoms together in a metallic substance. Such a solid consists of closely packed atoms and thus becomes a lot stronger)
Now, as the above methods can help an atom attain stability, what about those elements who already have their valence or last shells completely filled (according to the quantum atom rule in which a shell can have "2n²" electrons only)?
What are those elements? They are nothing but the NOBLE GASES! Yes! They have their valence or the outermost shell completely filled with electrons. They neither want to lose nor they want to gain. So, does that mean they're stable? Yes! And that's the reason why Noble gases are stable. Because what is a chemical reaction in chemistry? Nothing but the exchange of electrons! Any reaction you name it, it has a game of electrons that are playing the chemical reaction. And because noble gases are stable and they don't need any electrons, there is no chemical reaction! Simple. And if we connect what we've learnt you now know -
What are noble gases? Low or no reactive gases.
Why are they non reactive? Because They're stable.
What is stability? And how are they stable? Stability is where there is no chemical reaction for the electron to do and it has all its COMPLETE valence electrons. Noble gases are stable because they have all the electrons a valence shell must have according to quantum mechanics. (The 2n² rule)
THE NOBLE GASES
1) HELIUM: Helium is the first noble gas and the 2nd element in our periodic table of elements.
.gif)
It has a chemical symbol - "He". It is an odorless, colorless and of course low reactive gas. It has 2 electrons in its shell. According to the 2n² rule, the first shell of any atom that needs to be stable must have 2 electrons. How? Let's see mathematically. "n" in the 2n² is nothing but the number of shells. If helium has 1 shell, then it should have 2 x 1² (here 1 is the first shell of the helium atom) which is equal to 2, and as helium is the second element in the periodic table, which clearly means helium has 2 electrons in its first shell. Well, it has only 1 shell which has all the necessary electrons that it needs to have, that is 2 electrons. That's why it is low reactive. In 1895, William Ramsay discovered the presence of Helium on Earth.
Some Helium Facts you should know -
*Helium is the second most abundant element in the universe and the second lightest element.
*It is known that Our Sun produces 700 million tons of helium every second!
*And Helium has the lowest boiling point among all the elements, that is -268.8 Degree Celsius.
2) NEON: Neon, the 10th element of the periodic table, is the 2nd noble gas in our list. It is represented by the symbol "Ne" and is a colorless and odorless gas. You must have heard of neon lights, haven't you?
Neon lighting consists of brightly glowing, electrified glass tubes or bulbs that contain rarefied neon or other gases. What is rarefied? Nothing but the gas in a low pressure than usual. A high voltage is applied to the electrodes present in the neon tube, causing it to emit light. And that's how, we all love neon lights!
Now let's talk about its atomic structure. As it is a noble gas, it has all the necessary electrons in its shell according to the 2n² rule that you've learnt in the previous section. So, neon has a total of 10 electrons, where 2, are present in its first shell and the other 8, are present in the second shell, thereby completing the octet and being stable. Octet in chemistry is nothing but the 8 electrons arrangement in the second shell of noble gases.
So we now know that neon is stable, and is of course not much reactive. Let's see some facts about Neon.
*Neon was first discovered in 1898 by William Ramsay (the one who also discovered Helium) And Morris Travers.
*Neon got its name from the Greek word "neos" meaning new.
*Neon is non flammable and is lighter than air.
3) ARGON: So, Argon is the 3rd noble gas on our list which has the atomic number 18. It is represented by the symbol "Ar".
It has total 18 electrons where the first shell has 2, second shell has 8 and the third shell has 8 electrons. Wait, what? If Argon has 8 electrons in its valence shell, then how is it stable? According to our 2n² rule, the third shell must have 18 electrons, isn't it? Then Why Is Argon Stable? See, our analogy worked with Neon and Helium. As we deal with more and more electrons in the noble gases, we start looking at the octet rule. You know what an octet rule is, don't you? Argon is stable just like Helium and Neon because it has 8 electrons in the 3rd shell which satisfies the octet rule and what does octet rule says, there must be 8 electrons in the valence shell to be stable, giving it the same electronic configuration as a noble gas.
Now Argon has a lot of uses as well - It is used within neon tubes for lighting as well. It is also used in healthcare industries, manufacturing industries etc. It has a lot of use in welding or cutting as well. Let's see some Argon Facts!
*Argon is the most abundant noble gas.
*It accounts for roughly 1 percent of the Earth's Atmosphere and roughly 2 percent of the Martian Atmosphere.
*Leaving water vapor, Argon is the third most abundant gas in our atmosphere.
4) KRYPTON: We have learnt about 3 noble gases - Helium, Neon And Argon.
From this element, if we try to understand why is it a noble gas as it doesn't have completely filled shells, we may not understand a bit. That's why instead of the main shells, we go to the quantum shells or the sub shells which clears all our doubts of why is that. There is something called electronic configuration of elements which tells us how evenly the electrons of that element is distributed. I will surely make a complete post on electronic configuration because this clears the root of all the doubts. The main shells, also known as K, L, M and N are where we see the electrons to be situated. But there exists sub-shells in which actually the electrons are there. They are the S, P, D and F shells.
Based on this, electronic configuration of several elements is written. So now, to avoid confusion, if any element is a noble gas, then it must have the S, P, D and F shells or the subshells to be completely filled.
We write the configuration as - the number of shells with the name of the shell (S, P, D and F) And how much does the shell carries.
Mind you, the "S" shell carries only 2 electrons, the "P" shell carries 6 electrons, the "D" shell carries 10 electrons and the "F" shell carries 14 electrons.
And, the first shell has only the "S" shell, the second shell has the "S" and the "P" shells, the third shell has the "S" and the "P" and the "D" shells, while the fourth shell has the "S" and the "P" and the "D" and the "F" shells (all shells) present.
Let's take an example - The configuration of Krypton is - 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6.
Here above, all the red coloured numbers show the number of electrons the s, p and d shells carry. If we add all the red coloured numbers, we get 36, which is the atomic number of Krypton. As all shells are complete, Krypton is a noble gas. So, if you were wondering where were we going all this time, then it was just to prove that Krypton is a noble gas as all its SUBSHELLS ARE COMPLETELY FILLED.
If you do not understand any thing, no problem, I'll make a dedicated post on this topic. Or if any further doubts, then please contact.
Krypton is also used in light industries like energy saving fluorescent lights.
Let's see some facts-
*Krypton is a little, very very little reactive as well! It can react with fluorine to make Krypton fluoride.
*Krypton, also known as Super Man's Home planet, is the rarest gas on earth comprising 1 in a million part of the atmosphere.
*By the way, if you have noticed, Krypton also follows the octet rule, that is, Krypton also has 8 valence electrons.
To know about valency, click here - Valency
5) XENON: The fifth noble gas, Xenon also follows the octet rule for noble gases, that is, it also has 8 valence electrons. Xenon's atomic number is 54. So its electronic configuration is:
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6
.gif)
Post a Comment