Question

(a) 1. Which element is used in the lining of the special aprons worn by workers in nuclear power plants?
2. Why is this element preferred?
(b) \(^{24}_{11}\)Na emits a nuclear radiation which does not alter the mass number and is deflected by a magnetic field.
1. Name the type of nuclear radiation emitted by \(^{24}_{11}\)Na.
2. Write the equation for this radioactive decay.

Hint:

Remember the changes for nuclear decays: Alpha decay (\(A-4, Z-2\)), Beta decay (\(A\) unchanged, \(Z+1\)), Gamma decay (\(A, Z\) unchanged).

Answer 1

a(i)
Step 1: Understanding the Concept:
Nuclear radiation (like Gamma rays) can easily penetrate most materials and damage human tissue. Shielding is required using materials that can effectively absorb or scatter these high-energy photons.
Step 2: Detailed Explanation:
Lead is the standard material used for radiation shielding in medical and nuclear fields. Workers wear aprons lined with lead (lead aprons) to protect their internal organs from accidental exposure to ionizing radiation.
Step 3: Final Answer:
The element used is Lead.
a(ii)
Step 1: Understanding the Concept:
The absorption of high-energy radiation depends on the interaction of photons with electrons. Denser materials with more electrons per atom provide better protection.
Step 2: Detailed Explanation:
Lead is preferred because:
1. High Density: Lead is very dense (\( 11.3 \text{ g/cm}^3 \)), meaning atoms are packed closely together, leaving very little space for radiation to pass through without collision.
2. High Atomic Number (Z = 82): A high atomic number means each atom has many electrons. High-energy radiation interacts more frequently with these electrons via the photoelectric effect and Compton scattering, thus getting absorbed effectively.
Step 3: Final Answer:
Lead is preferred due to its high density and high atomic number, which enable it to absorb harmful ionizing radiation effectively.
b(i)
Step 1: Understanding the Concept:
Radioactive decay involves the emission of Alpha, Beta, or Gamma radiation. These are distinguished by their charge and their effect on the nucleus.
Step 2: Detailed Explanation:
1. Alpha (\( \alpha \)): Reduces mass number by 4. Deflected by magnetic field.
2. Beta (\( \beta \)): Consists of electrons (\( \beta^- \)) or positrons (\( \beta^+ \)). It has negligible mass, so it does not alter the mass number. Because it is charged, it is deflected by a magnetic field.
3. Gamma (\( \gamma \)): No change in mass or atomic number. Not deflected by magnetic fields (neutral).
The description provided matches the properties of Beta radiation.
Step 3: Final Answer:
The type of nuclear radiation emitted is Beta radiation.
b(ii)
Step 1: Understanding the Concept:
During Beta-minus decay, a neutron inside the nucleus transforms into a proton. This increases the atomic number by 1 while keeping the mass number constant.
Step 2: Detailed Explanation:
Parent Nucleus: \( ^{24}_{11}Na \)
Mass number (\( A \)) = 24 (stays the same)
Atomic number (\( Z \)) = 11 (increases by 1 \(\rightarrow\) 12)
The element with atomic number 12 is Magnesium (Mg).
The particle emitted is an electron (\( ^{0}_{-1}e \) or \( \beta^- \)).
The decay equation is:
\[ ^{24}_{11}Na \rightarrow ^{24}_{12}Mg + ^{0}_{-1}e \]
Step 3: Final Answer:
The radioactive decay equation is \( ^{24}_{11}Na \rightarrow ^{24}_{12}Mg + \beta^- \).