Question

Which from following instruments is used to determine the crystal structure?

• A. Scanning electron microscope
• B. FTIR spectrophotometer
• C. X-ray diffractometer
• D. Transmission electron microscope

Hint:

Whenever a question asks about exploring solid-state crystal lattices, atomic packing coordinates, or unit-cell dimensions, look directly for X-ray diffraction techniques (XRD). Crystallography and X-ray diffraction are fundamentally intertwined.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks to select the specific scientific instrumentation technique employed to investigate, solve, and accurately determine the internal atomic crystal lattices of a solid substance.

Step 2: Detailed Explanation:
Let us review the primary functions of each analytical option provided:

Scanning electron microscope (SEM): Primarily captures high-resolution topographic images of a specimen's surface morphology rather than mapping internal atomic spacing.

FTIR spectrophotometer (Fourier-Transform Infrared): Used to scan vibrational modes within chemical groups to identify functional bonds and molecular structures.

X-ray diffractometer (XRD): Operates directly on the fundamental principles of Bragg's Law:
$$ 2d\sin(\theta) = n\lambda $$ When a highly coherent beam of monochromatic X-rays hits a crystalline solid grid, the neatly spaced atomic planes scatter the waves, creating distinctive constructive interference arrays. Measuring these distinct diffraction patterns allows researchers to precisely measure interplanar distances ($d$) and reconstruct the entire three-dimensional crystal architecture.

Transmission electron microscope (TEM): Passes electron streams through ultra-thin samples to capture exceptional microstructural and internal morphological views, but it is not the baseline instrument dedicated to structural crystallographic matrix determinations.
Therefore, an X-ray diffractometer is the dedicated instrument for determining crystal structures.

Step 3: Final Answer: The proper instrument configuration matches option (C).