This video is on the topic of the noble gases. So what are the noble gases? The noble gases can be found on the very right hand side of the periodic table.
They are also referred to as group 0 or group 8 elements. The noble gases include helium, neon, argon, krypton, xenon and radon. They are all non-metallic elements which exist as single atoms.
So we say that they are monatomic. They are colourless gases, so they have low melting points and boiling points. The most important property of noble gases that you need to know is that they are unreactive and do not form molecules easily, so they are chemically inert.
It is important that you know in which group of the periodic table the noble gases can be found. You need to be able to explain why the noble gases are unreactive, and to do this we need to look at their electronic configurations. So let's focus on the first three noble gases. Helium has two electrons which occupy the first electron shell. Remember that the first electron shell can only hold up to two electrons, so this first shell is complete.
Neon has a total of 10 electrons, two in the first shell and eight in the second shell, so the second shell is complete. Argon has a total of 18 electrons, 2 in the first shell, 8 in the second shell and 8 in the third shell, so it too has a full outer shell of electrons. So they all have a full outer shell of electrons.
Remember a full outer shell of electrons is a stable arrangement and that the reason atoms react is to obtain a more stable arrangement. As the noble gases already have this, they are unreactive. In fact all of the noble gases have 8 electrons in their outer shell. with the exception of helium, which has two electrons. Let's look at a typical exam question about the noble gases, which focuses on reactivity.
The command word in this question is explain, so you need to state what the chemical reactivity of xenon is, and give a reason for its reactivity. Let the number of marks available guide you to the amount of detail that is required. It is a sensible assumption that one mark is available for stating that xenon is unreactive. So the second mark must be for the reason.
You always need to refer to the outer shell of electrons when explaining how reactive an element is. As xenon is unreactive, you need to explain that it has a full outer shell of electrons. There are other ways of wording this answer that would be acceptable for the second mark, which are that xenon has a stable electron arrangement or that it has eight electrons in its outer shell. This exam question is more applied.
The command word in this question is suggest. This means that you haven't specifically learned about this, but you should be able to apply your knowledge to this unfamiliar situation. When you are asked why a substance is used in a particular application, always give a property of that substance that makes it useful in that situation.
The main reason noble gases are chosen to be used in most applications is because of their unreactivity. And this is the property of noble gases that you are expected to know. Now you need to explain why that property of argon is useful in this situation, and that is because it won't react with the tungsten wire within the light bulb. Note how you must refer to tungsten specifically to be awarded this mark, so your answer needs to refer to the application that you were given.
As the question asks you why argon is used instead of air, you also need to refer to why air is not used. So the final mark is to explain what would happen if air was used instead of argon. Remember that metals will react with oxygen which is present in the air to form a metal oxide.
When tungsten reacts with oxygen, it is oxidized, so you would also be awarded the mark for stating this. In summary, the noble gases are non-metals which are monatomic. This means they exist as single atoms. They are unreactive as they have a full outer shell of electrons, which is a stable arrangement. They all have eight electrons in the outer shell, with the exception of helium, which has two electrons in its outer shell.
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