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 Define the term ‘Fissile Isotopes’.
Materials like 235U which can undergo fission directly with slow neutrons are known as fissile materials or fissile isotopes. Two important examples of fissile materials are 239Pu and 233U.
Write what do you understand by Nuclear reaction?
It is a kind of furnace for carrying out the controlled fission of radioactive material for producing power. Cadmium rods are used to control the chain reaction.
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What is α-particle?
It is the helium nucleus with two units of positive charge and four units of mass.
Between α- and β-rays, which has greater ionizing power?
Ans: α-particles
A nucleus has mass number 223. What is its mass number after one α-radiation?
After α-radiation, the mass number of the daughter element will be 219.
What advantage do protons have over α-particles as nuclear projectiles?
Both are positively charged and can be repelled by the nucleus. Proton being lighter can attain better speed than α-particles.

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Between α- and β-rays, which has greater ionizing power?

As neutrons are neutral, they do not experience any repulsion from the positive nucleus whereas protons being positively charged will be repelled by the positive nucleus.
How fusion and fission reactions produce large quantities of energy?
During the fusion and fission reactions, some mass of the reactant is lost and converted into the huge amount of energy according to Einstein mass-energy relationship.

Why all naturally occurring elements beyond lead in the periodic table are radioactive?
Naturally occurring elements beyond lead have a high value of n/p. Their nuclei become unstable and spontaneously disintegrate.
State group displacement law.
When a radioactive element loses an α-particle, the daughter element formed has a mass number less by 4 and atomic number less by 2 and occupy position two columns on the left of its parent element. The emission of β-particle forms a daughter element with atomic number raised by one and its position is one column on the right of its parent element.

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What is the mass defect?
Mass defect is the difference between the sum of the masses of the constituents of an atom of the element and its actual mass. It is measured in amu.
What is carbon dating?
Carbon dating is a process of determining the age of dead fossil or wood by comparing the activity of radioactive C-14 in the sample and the living plant.

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Write three differences between nuclear reaction and chemical reactions.
Nuclear reactions
(i)                  The particles present in the nucleus undergo a change.
(ii)                These reactions are irreversible.
(iii)               These are not affected by temperature and pressure.
Chemical Reactions
(i)                  Only valence shell electrons are involved in the chemical reaction.
(ii)                Chemical reactions may be reversible or irreversible.
(iii)               These are greatly affected by the change in temperature and pressure.

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