MATLAB: Undefined function or variable in MATLAB

Question

I have this function saved as element.m Whenever I call on it I say element(Hydrogen) I am trying to get it to display the name, symbol, atomic number, category, … But it keeps saying Undefined function or variable 'Hydrogen' I don't understand why its doing this.

function [Name, Symbol, Atomic_Number, Category, Proton, Neutron, Electron]=element(e)
%Inputs:
%e - 'Hydrogen' ;
%Outputs:
%Name
%Symbol
%Atomic_Number
%Category
%Proton
%Neutron
%Electron
e=[Hydrogen Helium]
if e=='Hydrogen'
  Name='Hydrogen';
  Symbol='H';
  Atomic_Number='1';
  Category='Nonmetal';
  Proton='1';
  Neutron='';
  Electron='1';
elseif e==Helium
  Name='Helium'
  Symbol='H'
  Atomic_Number='1'
  Category='Noble Gas'
  Proton='4'
  Neutron='2'
  Electron='4'
end 
end

Answer 1

What is e=[Hydrogen Helium] intended to do?