The Solid State

Question 69

What is the co-ordination number of each ion in Na2O.

The coordination number of Na in Na2O is 4.Na+ ion is surrounded by four oxide ion and O2- ion is surrounded by eight Na+ ions.
 Co-ordination number of Na
+ = 4.
Co-ordination number of O2– = 8.
Question 70

Why is an ionic crystal of NaCl a nonconductor explain?

ionic bonds are the electrostatic force of attraction between oppositely charged ion. The oppositely charged ion are arranged in a regular way to form giant ionic lattices. Ionic crystal of NaCl is a non-conductor of electricity because it has its electron in fully filled lower energy state. There are no free electrons in crystal lattice.
Question 71

What causes the conduction of electricity by semi-conductors?

 The conduction of electricity in semi- conductors is because of the  Electrons and holes.
Question 72

What may be the difference between phosphorus doped and gallium doped semiconductors?

Phosphorus doped semiconductors produced n- type semiconductor while when silicon doped with gallium, it produces p- type semiconductor.

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