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1. Why do Helium, Neon and Argon have a zero valency?
 
Helium has only , which is completely occupied by electrons. Argon and neon both have electrons in their outermost shell, which is the maximum number that can be accommodated in the outermost shell; thus, their valency is zero.
  
2. What were the drawbacks of Rutherford’s model of an atom?
 
Any particle moving in a circular motion will accelerate and emit energy. As a result, the circling electron loses energy and eventually falls into the . Thus, the atom should be . The model did not show any electron arrangement around the nucleus.