Aqa a level chem help

A sample of tin is analysed in a time of flight mass spectrometer. The sample is ionised by electron impact to form 1+ ions.
The table below shows data about the four peaks in the spectrum
m/z percentage abundance
112 22.41
114 11.78
117 34.97
120 to be determined
Give the symbol, including mass number, of the ion that reaches the detector first.

How do I find out the symbol? I know it’s the lightest mass but why would it be Sn and not Cd

A sample of tin is analysed in a time of flight mass spectrometer. The sample is ionised by electron impact to form 1+ ions.
The table below shows data about the four peaks in the spectrum
m/z percentage abundance
112 22.41
114 11.78
117 34.97
120 to be determined
Give the symbol, including mass number, of the ion that reaches the detector first.
How do I find out the symbol? I know it’s the lightest mass but why would it be Sn and not Cd

so its Sn becuase it says tin in the question,and its not Cd because 112 is just an isotope of tin, so this isnt the actual mass number but just the mass of one of its many isotopes if that makes sense, if not lmk

It says in the question that the element is tin in the first sentence, so looking up the chemical symbol of tin on the periodic table, you find it’s Sn.