Which of the following statements is evidence for the existence of ions in ionic
A Ionic compounds, in the solid state, conduct electricity.
B When any ionic compound in solution is electrolysed, the migration of ions
can be seen.
C In electron density maps for ionic compounds, there is no single line
representing electron density that surrounds both cations and anions.
D In electron density maps for ionic compounds, there are some single lines
representing electron density that surround both cations and anions.
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A clear demonstration of the existence of ions in solids is obtained from the electron density maps made on the basis of their X-ray analysis. The contour lines depict regions of equal electron density. Existence of regions of charge which are clearly isolated and segregated from other regions of charge confirms the presence of ions in the solid. In other words, in electron density maps, there should be no single line representing electron density that surrounds both cations and anions.
Another trivial method of demonstrating the presence of ions is electrolysis (in solution or in molten state). Solid ionic compounds never conduct electricity. Conduction of current through solution and subsequent discharge of ions in the electrodes is sufficient proof of existence of ions in solution. The ions are very very small species and hence the migration of ions in solution is never visible applying any technique, whatsoever.
The correct option is thus, C).
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