Carbon group

CO is highly stable,,aieee said how..

have a look at this --

Stability of Silicon Monoxide
To The Editor:
An error in the article entitled Speciality chemicals by
John Haschke [J. Chem. Educ., 52, 157 (1975)] should be
corrected. Silicon monoxide solid is not only preparable in
the laboratory, but it is available commercially in ton lots.
It is not stable between 1150 and 1300°C, but is thermodynamically
unstable at all temperatures.' However, like metastable
carbon monoxide solid, it can be quenched from the
gaseous phase. Both carbon monoxide gas and silicon monoxide
solid will disproportionate upon heating above room
temperature, especially in the presence of appropriate catalysts,
hut properly prepared silicon monoxide solid can be
retained at room temperature indefinitely.
Leo Brewer
University of California
Berkeley, California 94720

i guess its because of the size factor.the size difference between si & o will not allow strong overlapping of the p orbitals responsible for pi bonds.