The correct statement among the following is:

1.	Silicon exhibits 8 coordination numbers in its compound.
2.	The bond energy of F2 is less than Cl2.
3.	Mn(III) oxidation state is more stable than Mn (II) in an aqueous state.
4.	Elements of 15th gp show only + 3 and + 5 oxidation states.

Incorrect statement among the following is:

In X- H ----- Y, X, and Y both are electronegative elements. The correct statement among the following is:

Nitrogen form $N_2$, but phosphorous  form $P_2$, it's at a time convert in $P_4$, reason is:

1. Triple bond present between phosphorous atoms. 
2. $\mathrm{p}\mathrm{\pi }-p\mathrm{\pi }$ bonding is weak in phosphorous.
3. $\mathrm{p}\mathrm{\pi }-p\mathrm{\pi }$ bonding is strong in phosphorous.
4. Multiple bonds easily form phosphorous.

NH₃ forms a hydrogen bond but PH₃ does not because:  

Nitrogen exists as a diatomic molecule and phosphorus as P₄ because on moving 

A chemical that depletes the ozone layer is:

1. Sulphur

2. Chlorofluorocarbons (CFCs)

3. Nitrogen

4. Hydrogen

Fluorine forms only one oxoacid, HOF because of -

1. Low electronegativity and small size

2. High electronegativity and small size

3. High electronegativity and big size

4. Low electronegativity and big size

Oxygen forms hydrogen bonds while chlorine does not, because :

The uses of ${\mathrm{ClO}}_2$ is /are-

1. It is used for purifying water

2. It is used as a bleaching agent

3. Both '1'and '2'

4. None of the above