If the mass defect of ${ }_{5}^{11}B$ is $0.081 \ u$, its average binding energy (in $MeV$) is

Which of the following statements about radioactivity of an element is incorrect?

The atomic mass of lead is $208$ and atomic number is $82$. The atomic mass of bismuth is $209$ and atomic number is $83$. The ratio of $n/p$ in the atom is

Radioactive disintegration differs from a chemical change in being

The binding energy of $_8O^{16}$ is $127 \ MeV$. Its binding energy per nucleon is ...... $MeV$.

Calculate the mass defect in the following nuclear reaction:
$_1H^2 + _1H^3 \to _2He^4 + _0n^1$
(Given: mass of $_1H^2 = 2.014 \ amu$,$_1H^3 = 3.016 \ amu$,$_2He^4 = 4.004 \ amu$,$_0n^1 = 1.008 \ amu$) (in $amu$)