Question

An element X has the symbol ₈₄X²⁰². It emits an alpha-particle and then a beta-particle. The final nucleus is _bY^a. Find a and b.

Answer 1

\[\ce{_{Z-2}X^{A-4} ->_{Z-1}Y^{A-4} + _-1e^0}\] (β-emission)

\[\ce{_84X^202->_82X1^198 + _2He^4}\] (α- particles)

\[\ce{_82X1^198 -> _83Y^198 + _-1e^0}\] (β-emission)

\[\ce{_bY^a = _83Y^198}\]

∴ a = 198 and b = 83