Questions & Answers

Atomic radius is measured by:
A.Rutherfords ${{\alpha }}$- ray scattering experiment
B.X-ray diffraction technique
C.Millikan’s oil drop method
D.Thomson's water-melon model

Answer Verified Verified
Hint: The atomic radii’s values, which is approximately \[{\text{2 - 3}}{{\text{A}}^{\text{o}}}\], and is in the range of an X-rays wavelength.

Complete step by step answer
-The atomic radius of an atom is defined as the distance from the center of the nucleus to the outermost shell of the atom containing electrons i.e, the valence shell. Atomic radius can be measured by either the X-ray diffraction method or some other spectroscopic methods.
-When the size of the atom was determined by using the X-ray diffraction method, it was found that all atoms of the same element have the same radii.
-In X-ray diffraction, a beam of X-rays is directed towards the crystal and it interacts with the electrons of the atoms, the electrons start oscillating now and it begins to emit electromagnetic radiation. This wave emitted by the electrons has the same frequency as the X-rays. Now, the atoms in the crystal cause diffraction of the X-ray. The X-ray diffraction occurs when the scattering of the radiation occurs coherently.

Thus, the correct option is (A).

 Mainly, the atomic radius cannot be determined precisely due to some of the reasons listed below:
-We cannot accurately measure the size of the atoms because the electron cloud surrounding the atom does not have a sharp boundary.
-Another reason is that it is very difficult to isolate a single atom to determine its radius.
-Again the probability distribution of electrons of an atom is always affected by the presence of other atoms within the molecule or its surroundings. When an atom is present in different bonded states, its atomic radius can be changed. Thus, all these reasons can affect the measurement of atomic radii.
-But above all atomic radius has an important role in determining the chemical properties of elements. Mainly there are three different atomic radii used depending upon whether the element is a metal or a non-metal. They are covalent radius, van der Waals radius, and metallic radius.