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Look back to the ethyne page if you need to.

You will get a sigma bond on the line between the two nuclei, and two pi bonds formed by sideways overlap between p orbitals on the carbon and nitrogen. That nitrogen is now going to join to a carbon with a hydrogen attached - basically the left-hand side of the ethyne molecule you will have read about, giving HCN. So the diagam you last saw on the ethyne page, only differs because one of the green hybrid orbitals (say the right-hand one) contains a lone pair and won't take any further part in the bonding. You are counting the number of orbitals hybridised, not the number of electrons. Notice this is still called sp (or sp 1) hybridisation even though one of the orbitals contains 2 electrons. I can't honestly see this mattering, but if in doubt in an exam, follow the syllabus! The syllabus simply talks about sp hybrides. Note: Two points: To maintain consistency with the other sorts of hybridisation, I prefer the older term sp 1 hybrids. Unlike the carbons in ethyne, one of the hybrid orbitals contains a lone pair of electrons. Just like the carbon atoms in ethyne, this hybridises to give two sp 1 hybrids, leaving two of the p orbitals unchanged. Putting the outer electrons in boxes, you have Nitrogen has the electronic structure 1s 22s 22p x 12p y 12p z 1. You may need to keep referring back to the ethyne page during what follows. The bonding in ethyne (acetylene) isn't required by the syllabus, but is really useful to understand it because it helps you to work out the bonding in two molecules in statement 3.4.2(b) which I haven't discussed anywhere on Chemguide - HCN and N 2. Now go on to look at the formation of sp hybrid orbitals by reading the page about bonding in ethyne. The formation of pi bonds in triple bonds Don't go on to ethyne (below) until you are sure that you understand ethene. Now read the page about bonding in ethene.īy the time you have finished this page, it is really important that you understand the difference between a sigma bond (formed by end-to-end overlap between atomic orbitals) and a pi bond (formed by sideways overlap). The formation of pi bonds in double bonds Because it is a simple overlap, what is formed is a sigma bond. When a hydrogen molecule is formed, the 1s 1 orbitals from the two hydrogen atoms overlap to form a new molecular orbital. The syllabus also mentions the formation of a sigma bond in H 2. If you have already read the whole of the covalent bonding page referred to in learning outcome 3.4.1, you will recognise the bit about methane.ĭon't go on to ethene (next link below) until you are sure that you understand about the formation of methane and ethane. This page (and the next three that you will find below) come from the organic chemistry part of Chemguide. The concept of hybridisation which you will meet in this topic isn't really very difficult, but you need to take your time over it.īefore you go on, you should find and read the statements in your copy of the syllabus.įirst, you should read the page which looks at bonding in methane and ethane. I am taking these together because they are covered in the same set of Chemguide pages. This statement explains what σ (sigma) and π (pi) bonds are and introduces the concept of hybridisation. Chemguide: CIE A level chemistry support: Learning outcome 3.4.2Ĭhemguide: Support for CIE A level ChemistryĬovalent bonding - σ (sigma) and π (pi) bonds