The atom is krypton and its symbol is Kr.
the mass number is 41 + 36 = 77
its charge is 0 as it is a noble gas.
He could be blindfolded and know which was his and which was his sister's. All he would need to do is pick them both up and if they were too big then pick them up one at a time. The lumber might make it harder to tell, but this is a question about physical properties.
So there is a change in mass which for the purpose of this question should be quite different. His sister's ought to be much lighter than his. He would find it easier to pick up.
Answer:
I thinks its they grow longer explaination: I have a massive brain
