[Music] hi and welcome back to free science lessons by the end of this video you should be able to describe the electronic structure of the group zero noble gases you should then be able to explain why group zero elements are unreactive and finally you should be able to describe how the boiling points of group zero elements vary down the group so far on this topic we've been looking at the periodic table in the last video we saw that we can arrange all the elements into groups with similar chemical properties now one really important group is group zero which is called the noble gases the original periodic table produced by Dimitri Mev did not feature group zero and that's because the noble gases were not fully discovered until after Mel have developed his table here's the first key fact about noble gases the noble gases are very unreactive elements and you need to be able to explain explain why they're unreactive let's start by looking at the first noble gas which is helium I'm showing you here the structure of an atom of helium now I should point out that I'm not showing neutrons as they're not relevant to this topic we can see that helium atoms have two electrons and these electrons are both in the first energy level now the first energy level can hold a maximum of two electrons so in helium this energy level is full atoms are stable when they have a full outer energy level so atoms of helium are stable in other words they will not react this shows the structure of an atom of neon which is also a group zero noble gas neon has 10 electrons there are two electrons in the first energy level and there are eight electrons in the second energy level now the second energy level can hold a maximum of eight electrons so you can see that in neon the second energy level is full so because neon has a full outer energy level neon is an unreactive element here's the structure of an atom of argon which is another group zero noble gas again we can see that orgon has eight electrons in its outer energy level so again because it has a full outter energy level oron is unreactive so here's the second key fact about the group zero noble gases all of the noble gases have a full outer energy level and this makes the noble gases unreactive okay I'm showing you here the boiling points of the noble gases notice that all of the noble gases have boiling points lower than room temperature and that explains why they're all gases at room temperature now the boiling point of the noble gases increase as the relative atomic mass increases in other words as we move down group zero so helium has a relative atomic mass of four and helium has the lowest boiling point Ron has a relative atomic mass of 222 and radon has the highest boiling point you'll find plenty of questions on this topic in my vision workbook which you can get by clicking on the link [Music] above