When sunlight passes through a prism, the different wavelengths separate into a spectrum of colors.
The molar mass is 242 g/mol (<span>241.8597 g/mol). There is a very good online service to calculate molar masses:
http://www.webqc.org/mmcalc.php
</span>
M(Cs)=133 g/mol
M(O)=16 g/mol
M(CsxOy)=298 g/mol
w(Cs)=0.89
w(O)=0.11
CsxOy
x=M(CsxOy)w(Cs)/M(Cs)
x=298*0.89/133=2
y=M(CsxOy)w(O)/M(O)
y=298*0.11/16=2
Cs₂O₂ cesium peroxide