how can cyanide be so poisonous if it composed of atoms that are so common? For example, carbon is one of the most important elements (atoms) in your body. Nitrogen makes up 80% of the air we breathe.

Question

chmvijay · Answer

The properties of atoms/elements differs from that of the molecules:)
that's why chemistry in interesting stuff :) with different arrangement of atoms  giving rise to different molecules with different properties though they have the same elements.
for example C2H6O though it has 2 C, 6 H and 1 O
it can be ethanol C2H5OH 
or it can be an ether CH3COCH3
the properties of both compound as mentioned will be different :) 
In  CN also though the C and N are only present the  formation of that molecule will have different properties then the individual atoms 
hope u get it :