Thank you for the opportunity to help you with your question!
atomic number=number of protons
In a neutral element the number of protons is equal to the number of electrons.
In an cation the charge shows how many electrons are lost. So according to the charge, He has lost 5 electrons and has -3 electrons. Something is wrong. The calculations are right, but you have to consider that He is a noble gas, so it doesn't exchange electrons anyway!
Neutral compounds in which helium is involved in chemical bonds do not exist. Also the reactivity of noble gases follows the order Ne < He < Ar < Kr < Xe < Rn.
Please let me know if you need any clarification. I'm always happy to answer your questions.
Nov 1st, 2015
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