Nuclei

Q1.The Q-value of a nuclear reaction is defined as the energy released in the reaction. For alpha decay of ²²⁶₈₈Ra: ²²⁶₈₈Ra → ²²²₈₆Rn + ⁴₂He, given masses M(Ra) = 226.02540 u, M(Rn) = 222.01750 u, M(He) = 4.00260 u, the Q-value is:

• A4.87 MeV
• B3.28 MeV
• C0.00530 u
• D9.65 MeV

Q2.A radioactive sample has activity 3.7 × 10¹⁰ Bq (1 Curie) and half-life 5.27 years. Approximately how many radioactive atoms are present? (1 year = 3.15 × 10⁷ s)

• A8.9 × 10¹⁸
• B3.7 × 10¹⁰
• C2.4 × 10¹⁷
• D1.6 × 10²²

Q3.In alpha decay, the daughter nucleus compared to the parent nucleus has:

• AZ decreased by 2, A decreased by 4
• BZ decreased by 1, A decreased by 1
• CZ increased by 1, A unchanged
• DZ decreased by 2, A decreased by 2

Q4.Which of the following statements about nuclear forces is correct?

• ANuclear force acts over long distances like gravity
• BNuclear force is always attractive and charge-dependent
• CNuclear force is short-range, charge-independent, and repulsive at distances < 0.8 fm
• DNuclear force is weaker than electromagnetic force at all distances

Q5.The nucleus of an atom consists of:

• AProtons and electrons
• BProtons and neutrons
• CNeutrons and electrons
• DProtons, neutrons, and electrons