Determining the Mass of a Selenium Ion in a Bainbridge Mass Spectrometer

[beanryu]

The electric field between the plates of the velocity selector in a Bainbridege mass spectrometer is 20 V/m, and the magnectic field in both regions is 10 T(out and inside the spectrometer). A stream of singly charged selenium ions moves in a circular path with a radius of 1 m in the magnectic field(after they come out from the spectrometer). Determine the mass of one selenium ion.

How do I get the mass when I don't know the charge?
I know that v=E/B and Forces equal but I just can't find M without knowing the charge.

 

[ZapperZ]

Unless it means something else, a "singly charged" ion means that an electron has been removed from the selenium atom valence shell. So yes, you do know the amount of charge on the ions.

Zz.

 

[beanryu]

THANX!
I think I need to polish my english reading ability!