Incorrect statement about peptide bond is:
 

1.	C–N bond length in proteins is longer than the usual bond length of N-bond.
2.	Spectroscopic analysis shows the planar structure of  group.
3.	C–N bond length in proteins is smaller than the usual bond length of the C–N bond.
4.	None of the above.

The bond angle is maximum in:

1. $N{H}_3$

2. $N{H}_4^{+}$

3. $PC{l}_3$

4. $SC{l}_2$

Among the following, the pair in which the two species are not isostructural is:

1. ${\mathrm{IO}}_3^{-}\text{and }{\mathrm{XeO}}_3$

2. ${\mathrm{BH}}_4^{-}\text{and }{\mathrm{NH}}_4^{+}$

3. ${\mathrm{PF}}_6^{-}\text{and }{\mathrm{SF}}_6$

4. ${\mathrm{SiF}}_4\text{ and }{\mathrm{SF}}_4$

In a regular octahedral molecule, MX₆, the number of X–M–X bonds at 180º is: