_____ number of protons are present in an element X with an atomic number Z and mass number A.
Atom A has a mass number 209 and atomic number 82.
Atom B has a mass number 209 and atomic number 83.
(i) How many protons atom A has ?
(ii) How many protons atom B has ?
(iii) Are atoms A and B isotopes of the same element ?
An element has atomic number 19 and mass number 39. How many electrons and protons are present in its unipositive ion?