The Solid State

Question 173

Explain the following with suitable examples:
Antifluorite structure 

Antifluorite structure: 
The antifluorite structure is the opposite arrangment with anion in FCC array with coordination number 8 and cation in the tetrahedral holes with coordination number 4. example of the antifluorite structure are K2O, LiO, Na2O and K2S.
Question 174

Give reasons for the following:
Molecular solids are generally soft and easily compressible.

A molecular soild consist of small, non-polar covalent molecule and is held together by landon dispersion forces. thus the force of attraction between the molecule is less de to this reason molecular soilds are generally soft and easily compressible.
Question 175

Give reasons for the following:
The energy required to vapourise one mole of copper is smaller than that of energy required to vapourise one mole of diamond.

The bonding have great influence on the any substance. Copper is a metallic solid having metallic bonds while diamond is a covalent solid having covalent bonds. Metallic bonds are weaker than covalent bonds thus lesser amount of energy is required to break metallic bonds than covalent bonds.
Question 176

Give reasons for the following:
All metals have metallic bonds but some metals are soft and having low melting points and some are hard and having high melting points.

The strength of metallic bond depends upon the numbr of valence electrons of the metal atom and the magnitude of forces binding these electrons to the nuclei. Thus the strength of metallic bond in different metals may be weak or strong, hence their nature (soft or hard) and their melting points may be different.

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