What is the significance of the x in the chemical formula (Mo6S9-xIx)?

[lo2]

On

http://en.wikipedia.org/wiki/Nanowire"

This sentence.

For example, inorganic molecular nanowires (Mo6S9-xIx) have a diameter of 0.9 nm, and can be hundreds of micrometers long.

What is (Mo6S9-xIx) I know it is a chemical formula for a molecule but what do those x'ses mean?

 

[geoffjb]

On

http://en.wikipedia.org/wiki/Nanowire"

This sentence.

For example, inorganic molecular nanowires (Mo6S9-xIx) have a diameter of 0.9 nm, and can be hundreds of micrometers long.

What is (Mo6S9-xIx) I know it is a chemical formula for a molecule but what do those x'ses mean?

It appears to be written Mo₆S_9-xI_x. In that case, the wire would contain x atoms of I and 9-x atoms of S.

For example, 6 I atoms would yield Mo₆S₃I₆. It probably has to do with molecular packing.

 

[Gokul43201]

The index "x" is used to refer to a series of compounds with the same elements (and likely, identical crystal structures) but different stoichimetric ratios between the elements. Very likely, you will find that the original source of any study on these compounds will specify the range of values that x was made to take in the experiment. You can then plug in those values and calculate the compositions as geoff has shown above.

Extra note: Since Iodine is about 30% bigger than Sulfur, I don't imagine you can vary x by a whole lot (maybe a range of 1 or 2) without introducing large strains that will destabilize the wire.