α-particles do more damage inside the body than β-particles. Why? Is it also true when the body is exposed to the external source of such radiations?
When absorbed by human tissues, α-particles do more damage than β-particles due to their greater ionizing power. But if exposed to such radiation, they cause less damage since they are not easily absorbed by human body.
The stability of a radioactive substance is related to its half life period. Explain.
It is true. We know that shorter the half life period of an element, greater is the number of atoms undergoing disintegration and lesser is the stability of radioactive substance. The half life period of Ra-224 and Ra-226 are 3.64 days and 1590 years respectively. Thus, Ra-224 is least stable where Ra-224 is most stable Isotope.
What correction should be made to the isotopic mass of the chlorine 1735Cl atom before the mass defect of the chlorine nucleus can be calculated.
In order to get the mass of chlorine nucleus, the mass of 17 electrons should be subtracted from the isotopic mass of chlorine.
Can y-rays emerge from a natural radioactive element before the emission of α- and β-particle.
Y-rays are emitted when the excited nuclei after the loss of α-particle and β-particles return to their ground state. Hence, y-rays are not emitted prior to the emission of - and β-particles.
What is melt down?
It is a serious type of nuclear accident in which the fuel core melts and as a result its container melts. This situation arises when too many neutrons initiate a fission reaction so that more heat is built up than that can be away.
What is the S.I, unit of Radioactivity?
             The S.I. unit of Radioactivity is Becquerel.
Why are all the natural occurring elements beyond lead in the periodic table radioactive?
                The n/p ratio for the element beyond lead is more than 1.5. So, they have unstable nuclei and hence radioactive.
What is shortest distance between the nuclear particles at which the nuclear attractive force is maximum?
                The shortest distance is 8×10-14 cm at which nuclear attractive force is maximum. The force decreases if the distance is less or more than 8×10-14 cm.

Is there any difference in the radioactivity of a radio element and its compound?
                The radioactive properties of a radio element are similar to the properties of its compounds. The reason is that it is a nuclear phenomenon.
What do you know of binding energy per nucleon?
                It is obtained by dividing the binding energy by mass number. Greater the value of binding energy per nucleon, more stable the nucleus is.
What are magic numbers?
                There are the numbers 2, 8,20,50,82 and 126. Nuclides having magic number of either protons or neutrons or both are more stable. Nuclides with atomic number equal to magic number have more number of stable isotopes than their neighbours.





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