Why sulphur monoxide is unstable

Basic idea on why a substance cannot stably exist:

It is impossible to determine the absolute stability of a substance. However, if a substance spontaneously (自發地) changes to other substance(s), this substance is unstable and cannot exist.

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Consider the following reaction:
2SO → SO2 + S
or 2S=O → O=S=O + 2S

Obviously, there are 2 moles of S=O bonds on the left hand side, and there are 2 moles of S=O bonds and a number of covalent bonds in 2 moles of S on the right hand side. Obviously, [SO2 + S] is much more stable than SO, and thus SO would spontaneously changes to SO2 and O2. In other words, SO is unstable and cannot exist.

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You can use similar argument to show that CS is unstable and does not exist. Also, you can think about more unstable compound in the same way.

the bonding of sulphur monoxide is
S=O
it is a planar structure.
but for sulphur it is formed by the hybridization of
3s and3p orbitals.
but for oxygen it is formed by the hybridization of
2s and 2p orbitals.
so the hybridized orbitals are not stable.
so sulphur monoxide is also not stable too.

2008-06-03 08:39:36 補充：
should be linear structure.