Chemistry Class 11 NCERT Solutions: Chapter 11 the p Block Elements Part 2

Q: 7. Describe the shapes of Equation and Equation . Assign the hybridisation of boron in these species.

Answer:

(i) Equation

As a result of its small size and high electronegativity, boron tends to form monomeric covalent halides. These halides have a planar triangular geometry. This triangular shape is formed by the overlap of three Equation hybridised orbitals of boron with the Equation orbitals of three halogen atoms. Boron is Equation hybridised in Equation .

(ii) Equation

Boron – hydride ion Equation is formed by the Equation hybridisation of boron orbitals. Therefore, it is tetrahedral in structure.

Q: 8. Write reactions to justify amphoteric nature of aluminium.

Answer:

A substance is called amphoteric if it displays characteristics of both acids and bases. Aluminium dissolves in both acids and bases, showing amphoteric behaviour.

(i) Equation

(ii) Equation

Q: 9. What are electron deficient compounds? Are Equation and Equation electron deficient species? Explain.

Answer:

In an electron-deficient compound, the octet of electrons is not complete, i.e., the central metal atom has an incomplete octet. Therefore, it needs electrons to complete its octet.

(i) Equation

Equation is an appropriate example of an electron – deficient compound. B has 3 valence electrons. After forming three covalent bonds with chlorine, the number of electrons around it increases to 6. However, it is still short of two electrons to complete its octet.

(ii) Equation

The electronic configuration of silicon is Equation this indicates that it has four valence electrons. After it forms four covalent bonds with four chlorine atoms, its electron count increases to eight. Thus, SiCl4 is not an electron deficient compound.

Q: 10. Write the resonance structures of Equation .

Answer:

(A) Equation

(B) Equation

There are only two resonating structures for the bicarbonate ion.

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