To determine that NH2- is polar or non polar,1st of all we need to define what is polar and non polar?

Polar molecules:

A polar molecule is that which has a net dipole as a product of the opposite charges (i.e. having partial positive and partial negative charges) from polar bonds set asymmetrically. Similar to a magnet having two poles, the polar molecules also hold two poles that grasp two opposite charges.

Nonpolar molecules:

A molecule is known as nonpolar when there is an equal sharing of electrons between the two atoms of a diatomic molecule or due to the symmetrical array of polar bonds in a extra composite molecule.

So, Is NH2- polar or nonpolar? Yes, NH2- is polar in natural history. Polarity is a chemical possession in which the separation of charges generates two poles (positive and negative) in a compound.

The Nitrogen atom is highly electronegative as compare to Hydrogen atoms due to which unequal sharing of charge exist on the atoms of nitrogen and hydrogen that consequence in a net dipole moment and bent shape of NH2- molecule. As a result, the NH2- (Amide ion) is polar molecule.

Properties of NH2- ion

  • The molecular mass of Amide ion is approximately 16.024 g/mol.
  • 8 valence electrons are present in NH2- molecule.
  • It is a monovalent ion and also recognized as Nitrogen Hydride.
  • Amide ion (NH₂⁻) is V shaped or bent shaped molecule.
  • In Amide ion (NH₂⁻) 2 pairs are bonding and 2 are non-bonding electrons.
  • The overall shape would be bent (angular) V shaped with 104.5 degree bond angles due to powerful lone pair-bonding pair repulsion that drive the 2 bonding pairs closer together than they would exist.
  • It has a hybridization of sp3 and it holds 2 lone pairs. So due to the repulsion between the two lone pairs this attain a shape of V.

Factors that affect polarity of NH2-:

The polarity of a molecule is reliant on various aspects. We will talk about them briefly.

Shape of NH2-

It is imperative to note down that lone pair-lone pair repulsion is larger than lone pair-bond pair and bond pair-bond pair repulsion. Correspondingly, the lone pairs present on the atom of Nitrogen forces the two bonds shaped among the Hydrogen and Nitrogen in the downward trend.

Due to lone pair-lone pair repulsion and lone pair-bond pair repulsion both the bonds bents in the downward direction ensuing in the bent V-shape (angular). It illustrates that NH2- is polar molecule.

NH2- Hybridization:

The molecule of NH2- has single Nitrogen and two Hydrogen atoms. In total, Amide ion consist 8 valence electrons in which two pairs are bonded as N-H bond and left behind remnants as two lone pairs on the Nitrogen atom.

The hybridization of a molecule can be resolute by a formula.

Formulae to calculate hybridization = 1/2(V + M -C +A)

Wheres:

M = no of monoatomic atoms linked with the central atom

V = valence electron of central atom

A = anionic charge

C =cationic charge

And, as we know that NH2- is an anion, therefore values are as below:

V= 5, M=2, C=0, A=1

Hybridization of NH2- ⇒ 1/2(5+2+1) = 4= sp3

Accordingly, the hybridization of NH2- is sp3. Sp3 hybridization demonstrate that molecule is polar.

Dipole moment:

A polar molecule always has a tendency to have a net dipole moment value. It is defined as a measure to find out the value of the polarity of a chemical bond involving two atoms. The electric dipole moment model is implicated in measuring the polarity.

D = q * r

D = dipole moment

q = charge

r = distance between the charges

Electronegativity:

The word electronegativity is also important factors that resolve the polarity of a molecule. In a molecule, if there is a distinction between electronegativities of the two atoms then the bond shared by them is polar.

Greater the electronegativities difference of two atoms greater is the polarity of the bond between them.

If electronegativity difference of two atoms is from 0.4 to 1.7 then it will be formed polar bond. If the electronegativity difference of two atoms is less than 0.4, then non polar bond will be formed.

The electronegativity of Nitrogen is 3.04 and Hydrogen is 2.2 so this difference makes the N-H bond polar.

Electronegativities difference of two atoms = 3.04-2.2= 0.84

This value proves that NH2- is polar molecule. The difference in electronegativities of Hydrogen and Nitrogen atom results in the unequal sharing of charges between the bonded atoms. Therefore, net dipole moments subsist for NH2- molecule. Therefore, Amide ion (NH2-) is polar in natural world.

For example, Oxygen molecule contains two Oxygen atoms having the same electronegativity, as a effect, there is an equal distribution of charge on the oxygen atoms. Consequently, it shows that Oxygen molecule is non-polar.

Symmetry:

This is also an essential factor for verifying the polarity of a molecule. Polarity can be calculated by just analyzing the geometrical arrangement of a molecule. If a molecule is symmetrical, the dipole moment turns out to be zero and we can pronounce that the molecule is non-polar.

Whereas the unsymmetrical molecules having a net dipole moment and making it a polar molecule.

So, in the case of Amide ion (NH2-), it is unsymmetrical molecule which makes it a polar molecule.

LEARN: C2H2 POLAR OR NONPOLAR