Solution
= Solution
Measure $x$ from the <carbon> nucleus toward the <sulfur> nucleus. The definition of the <center of mass> gives
$$
x_{\rm cm}=\frac{m_{\rm C}\,0+m_{\rm S}r}{m_{\rm C}+m_{\rm S}}.
$$
Therefore the requested distance is
$$
\boxed{r_1=\frac{m_{\rm S}}{m_{\rm C}+m_{\rm S}}r.}
$$
The other distance is $r_2=r-r_1=m_{\rm C}r/(m_{\rm C}+m_{\rm S})$, consistent with $m_{\rm C}r_1=m_{\rm S}r_2$.