question_answer

The atomic mass of lead is 208 and its atomic number is 82. The atomic mass of bismuth is 209 and its atomic number is 83. The ratio of neutrons/protons in the atom (a) higher of Pb                 (b) higher of Bi (c) same of both               (d) None of these

Answer:

Given mass number of lead\[={{A}_{Pb}}=208;\]              atomic number of lead\[={{Z}_{Pb}}=82\] \[\therefore \]No. of neutrons in lead\[={{n}_{Pb}}={{A}_{Pb}}{{Z}_{Pb}}=\] \[20882=126\] \[\Rightarrow \]\[{{(n/P)}_{Bi}}=\frac{126}{83}=1.51\]   _______ (1) Mass number of bismuth\[={{A}_{Bi}}=209\] Atomic number of bismuth\[={{Z}_{Bi}}=83\] \[\therefore \]No. of neutrons in bismuth \[={{n}_{Bi}}={{A}_{bi}}{{Z}_{Bi}}\] \[=20983=126\] \[\Rightarrow \]\[{{(n/P)}_{Bi}}=\frac{126}{83}=1.51\]   ________ (2) From (a) and (b) the n/p ratio of lead is greater.