Does sulphur dioxide show co ordinate covalent bonding or expanded orbital?
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Answers
Answer:It is best to say that SO2 has covalent bonds from the sulfur atom to each oxygen. In reality the wave-functions are quite complicated, and there are understandable simple approximate descriptions. A common one is in terms of molecular-orbital theory, but I will instead try a simple Lewis-like (resonating) VB explanation, depending on the Lewis octet rule -- which assigns a net closed- shell worth of electrons to each atom -- a closed shell having an octet of electrons for S & O (as well as for many other common low-atomic number atoms). For covalent bonds this involves sharing of electrons between 2 atoms.
An S atom has 6 valence electrons as does each O atom, so that each lacks 2 electrons in forming a closed shell. One can start by forming a double covalent bond between S & one O atom -- this entails 2 electrons from S & 2 from O, to be shared between the S & O, so that each has a net closed shell octet. The second O atom now forms an electron-pair bond with 2 electrons from the S & none from the O -- this shared electron pair bond is sometimes called a "coordinate covalent" bond -- and now the last O atom has a net closed-shell octet.
It is possible that a student might confuse this coordinate covalent bond with an ionic bond because of another way of representing it. In this alternative approach, instead of thinking of 3 neutral atoms, one thinks of 1 neutral O atom, 1 S + cation, & 1 O - anion: whence these 3 atomic moieties have 6, 5, & 7 valence electrons, and lack 2, 3, & 1 electrons from forming a closed-shell octet. Thence one forms a double covalent bond between S+ & O while one forms a single covalent bond between S+ & O-, to lead to closed-shell octets for everything. One might think of the last bond mentioned as half ionic & half covalent, but unlike ionic bonds are directed. And also resonance ideas apply so that the O & O- moieties can be interchanged, whence from this bonding scheme there is on-the-average half an ionic bond between S & each O while also there is 3/2 of a covalent bond between S & each O. This indicates a charge distribution of a net charge of -1/2 for each oxygen & +1 for the (central) sulfur.
A further point is that though each of the 3 neutral atoms has 6 valence electrons, the role played by S is much different than that played by O -- because O is much more electronegative than S -- which is to say that S donate electrons much more easily than O, and that O accepts electrons much more easily than S. With reference to neutral atoms, our simple bonding schemes identify 6 bonding electrons -- 4 from S and a net of 1 from each O. The distribution of charge from accurate developments of molecular wave-functions ends up with some excess electron charge (which is negative) on the O atoms and a corresponding (positive) electron deficit on the S atom.
Some summary points might be made. Neither of the 2 Lewis-like schemes are correct -- nor is the simple molecular-orbital explanation some authors present -- they are just rough approximations, which have been found to provide resemblances to empirical data and especially detailed wave-functions. The correspondences to wave-functions have not been given a generally accepted precise relationship -- basically because of the complexity of full high-quality wave-functions. It is actually amazing that a little qualitative Lewis-like consideration gives as much insight as it does. These ideas work quite well for 99+% of characterized stable organic molecules, which in turn constitute >90% of all characterized stable molecules. Even for the remaining non-organic molecules there is a notable tendency for these ideas to work -- as illustrated for SO2 -- and there are sensible guidelines for when it might work.
Answer:
yes sulphur dioxide shows co-ordinate bonding and also expand orbital because sulphur has vacant d-orbitals
Explanation: