CBSE Class 12-science Answered
(i) The total decay rate of a sample of one or more radionuclides is called the activity of that sample. The SI unit for activity is Becquerel, named after the discoverer of
radioactivity, Henry Becquerel.
(ii)
Variation of Activity of a given radioactive sample with time.
(iii)
In a decay an electron is emitted by the nucleus.
Therefore for D1 we can write
Mass number of D1 = Mass number of D2 = 176
Atomic number of D1 = Atomic number of D2 +1 = 71+1 = 72
In a decay the mass number and the atomic number of the daughter nucleus decreases by four and two, respectively.
Thus for D we can write,
Mass number of D = Mass number of D1 + 4 = 176 + 4 = 180
Atomic number of D = Atomic number of D1 + 2 = 72 + 2 = 74