[填空题]
Boron nitride is a solid material with a layered giant covalent structure. The structure of one layer of boron nitride is shown.
The structure of boron nitride is similar to that of a carbon allotrope.
1.Define the term allotropes.
2.State the name of the carbon allotrope that is structurally similar to boron nitride.The name is
3.Explain why the B atoms in boron nitride may be described as electron-deficient.
4.The N atoms in boron nitride form bonds with equal lengths and bond angles of 120$^{\circ}$.
1.The electron domain geometry around the N atom is .
2.Explain why the geometry named in (i) suggests that boron nitride contains dative covalent (coordination) B-N bonds.
3.Explain why the B-N bonds have equal lengths, despite the presence of the additional covalent bond named in (ii).
5.The layers of boron nitride are stacked as shown.
Boron nitride is than the carbon allotrope named in (b).
