Which pair of ions from the following list do not constitute an iso-electronic pair?

1. Mn²⁺, Fe³⁺

2. Fe²⁺, Mn²⁺

3. O^2-, F^-

4. Na⁺, Mg²⁺

The following graph captures potential energy on the y-axis for hydrogen gas formation as a function of the internuclear distance on the x-axis:
        
The bond energy of H₂ can be represented by-

The correct Lewis structure of acetic acid is:
 

1.		2.
3.		4.	None of the above.

The significance of the octet rule is:

1. To determine the stability of atoms.

2. To find the hybridization of elements.

3. To calculate the number of lone pairs.

4. None of the above.

The lone pairs of electrons can be defined as -

1. Electron pairs that participate in bonding.

2. Electron pairs  that do not participate in bonding.

3. Electron pairs that are present in inner most shell.

4.Electron pairs that are present in valence shell of ions.

CH₄ does not exhibit square planar geometry because:

The application of dipole moment is/are :

${\mathrm{H}}_3{\mathrm{PO}}_3$ can be represented by structures 1 and 2 shown below. 

These two structures cannot be taken as the canonical forms of the resonance hybrid, because  : 

1. The positions of the atoms have changed.

2. The positions of the atoms are constant.

3. H₃PO₃ does not show resonance.

4. Two hydrogen atoms are missing.

The bond length can be defined as -

The favourable factors for the formation of an ionic bond would be: