The radio active radiation used in studying the arrangement of particles in giant organic molecules is

Analysis

The question asks for the specific type of radiation used to determine the structural arrangement of atoms within complex (giant) organic molecules, such as proteins or polymers. This process is known as X-ray crystallography (or X-ray diffraction).

Concept Explanation

To study the arrangement of particles (atoms) in a molecule, the wavelength of the radiation used must be comparable to the distance between the atoms in the molecule (which is typically in the range of $10^{-10}$ meters or 1 Angstrom).

• X-rays have wavelengths in the range of $0.01$ to $10$ nanometers, which perfectly matches the inter-atomic spacing in crystals. When X-rays strike a crystal, they are diffracted by the atoms, creating a pattern that scientists can analyze to map out the exact positions of atoms in a giant molecule.
• $\alpha$-particles are heavy, positively charged helium nuclei that do not penetrate matter well enough for structural analysis.
• $\beta$-particles are high-energy electrons that are typically used for medical imaging or dating, but they are not suitable for diffraction studies of molecular structures.
• $\gamma$-rays have extremely short wavelengths and high energy; they are generally too penetrating and difficult to focus for the precise structural determination required for organic molecules.

Step-by-Step Solution

1. Identify the objective: We need a radiation type that can diffract off atoms to reveal their spatial arrangement.
2. Evaluate the options: • $\alpha$ and $\beta$ particles are matter particles, not electromagnetic waves, and are unsuitable for diffraction patterns of molecular structures. • $\gamma$-rays have wavelengths that are too short and energy levels that are too high, often causing damage to the sample rather than providing a clear diffraction pattern. • X-rays have the ideal wavelength to interact with the electron clouds of atoms in a crystal lattice.
3. Conclusion: X-ray diffraction is the standard scientific method for determining the 3D structure of giant organic molecules (like the famous discovery of the DNA double helix structure).

Correct Answer

The correct option is C.

Exam Tip

Whenever you see a question about "determining the structure of molecules," "crystal lattice," or "atomic arrangement," always look for X-rays or X-ray diffraction. It is a classic JAMB Chemistry topic!