State one observation which shows that atom is not indivisible.

(a) Name an element which does not contain neutron.

(b) If an atom contains one electron and one proton, will it carry any charge or not?

Name the sub-atomic particle whose charge is

(a) +1

(b) -1

(c) 0.

Which sub-atomic particle was discovered by

(a) Thomson

(b) Goldstein

(c) Chadwick.