Unstable nuclei attain stability through disintergration. The nuclear stability is related to neutron- proton ratio (n//p) . n//p ratio for stable nuclei lies quite close to unity for elements with low atomic numbers ( 20 or less) but it is more than one for nuclei having higher atomic numbers. Nuclei having n//p ratio either very high or low undergo nuclear transformation. (i) When n//p ratio is higher than required for stability, the nuclei have the tendency to emit beta -rays, i.e. a neutron is converted into a proton. (ii) When n//p ratio is lower than required for stability, the nuclei increase the ratio, either by emitting alpha -particle or by emitting a positron or by K -electron capture. Consider the following nuclear reactions, ""_(92)^(238)M to _(y)^(x)N+2_(2)^(4)He , ""_(y)^(x)N to _(B)^(A)L+2beta^(+) The number of neutrons in the element L is

Assertion (A) : Rutherford visualised the nuclear model of an atom. Reason (R) : Rutherford's atom model fails to explain the stability of the atom.

Unstable nuclei attain stability through disintegration. The nuclear stability is related to neutron proton ratio (n//p) . For stable nuclei n//p ratio lies close to unity for elements with low atmoic numbers (20 or less) but it is more than 1 for nuclei having higher atomic numbers. Nuclei having n//p ratio either very high or low undergo nuclear transformation. When n//p ratio is higher than required for stability, the nuclei have the tendency to emit beta -rays. while when n//p ratio is lower than required for stability, the nuclei either emits alpha -particles or a positron or capture K -electron. For reaction ._(92)M^(238) rarr ._(y)N^(x) + 2 ._(2)He^(4), ._(y)N^(x) rarr ._(B)L^(A) + 2 ._(-1)e^(0) The number of neutrons in the element L is