Question 1
5. Knowledge of atomic structure is fundamental to understanding the properties of the elements, chemical reactivity, and nuclear reactions.

(a) Around 1909 Rutherford and his researchers bombarded thin gold foil with positively charged alpha particles from a radioactive radon-222 source and observed their resultant pathways. Most alpha particles passed through the foil with no deflection or very slight deflections, a small number were deflected through large angles, and a very tiny number rebounded back along their original paths.
(i) Based on the model of the atom that Thomson had proposed after his discovery of the electron in 1898 , which one of these three observations was the most unexpected?
(ii) What conclusion did Rutherford reach about the structure of the atom from all of the observations in the gold foil experiments taken together?

(b) Define (i) isotopes, (ii) relative atomic mass.