Ionic crystals such as sodium chloride are hard and have high melting points because
- A. their ions are held by weak van der Waals forces
- B. strong electrostatic forces act between oppositely charged ions throughout the lattice
- C. they contain covalent bonds between the ions
- D. the ions are free to move at room temperature
Explanation
Every ion attracts all the oppositely charged ions around it, and a great deal of energy is needed to break this extended three dimensional network, so the melting point of sodium chloride is 801 degrees Celsius. The ions are locked in place in the solid, which is why solid sodium chloride does not conduct electricity while the molten salt and its solution do.
Related questions
Molecular crystals such as solid iodine have low melting points because
Which of the following is a covalent network solid?
Metals are malleable and ductile because
Which of the following solids is held together by dispersion forces only?
Solid sodium chloride does not conduct electricity, but molten sodium chloride does, because