NH2OH lewis structure, molecular geometry, and its bond angle

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NH2OH lewis structure molecular geometry

Hydroxylamine appears as vivid white, opaque crystals and has a chemical formula NH2OH or H3NO. It is used as an aqueous solution and an intermediate in biological nitrification. 

In this article, we will discuss H3NO or NH2OH lewis structure, molecular geometry, and its bond angle, etc.

Hydroxylamine is an unstable, odorless, and hygroscopic compound. It is commonly used as a nucleophilic reagent, reducing agents in organic and inorganic reactions.

Name of MoleculeHydroxylamine
Chemical formulaNH2OH or H3NO
Molecular geometry of NH2OHTrigonal pyramidal
Electron geometry of NH2OHTetrahedral
Nature Polar
Bond angle107º, 103.3º, 101.4º
Total Valence electron for NH2OH14

How to draw lewis structure of NH2OH?

NH2OH lewis structure has two N-H bonds, one N-O bond, and one O-H bond. The nitrogen is the central atom and there is one lone pair on it. The lewis structure of NH2OH has a total of 3 lone pairs and 4 bond pairs.

NH2OH lewis structure is drawn with the same procedure as the NH2Cl lewis structure.

Follow some steps for drawing the lewis dot structure for NH2OH

1. Count total valence electron in NH2OH

Valence electrons are found in the outer shell of the atom that can form a chemical bond with another atom. To get the total valence electron in NH2OH, look at the group number of individual atoms – nitrogen, hydrogen, and oxygen.

The nitrogen atom belongs to the pnictogens family and has a group number 15, hence, its valence electron is 5, the oxygen atom is situated in group number 16, hence, its valence electron is 6.

The hydrogen atom is situated in the first row of the Periodic Table and has period group number 1, hence, its valence electron is 1.

⇒ Total number of the valence electrons in nitrogen = 5

⇒ Total number of the valence electrons in hydrogen = 1

⇒ Total number of the valence electrons in oxygen = 6

∴ Total number of valence electrons available for the NH2OH Lewis structure = 5 + 1(2) + 6 + 1 = 14 valence electrons         [∴ NH2OH molecule has 1 nitrogen, 3 hydrogen and 1 oxygen atom]

Total number of valence electron available for the lewis structure of NH2OH

2. Find the least electronegative atom and place it at center

The best preferable element for the central position is the least electronegative atom in the molecule. But it should be noted that the hydrogen atom always goes outside in the lewis diagram because it can only make a maximum of one bond.

So, in the case of NH2OH, the hydrogen goes outside in the lewis diagram, and among nitrogen and oxygen, look at their electronegativity value.

The electronegativity of nitrogen is 3.04 and for oxygen, it is 3.44. Clearly, the nitrogen atom is less electronegative, hence, put the nitrogen atom in the central position and other atoms as shown in the figure given below.

central atom in NH2OH lewis structure

The nitrogen is in center, the two hydrogen either side of it and one hydrogen should attached to the oxygen atom, this will make OH group.

3. Connect outer atoms to central atom with a single bond

Draw the skeletal structure of NH2OH as shown below.

NH2OH skeletal structure

Look at the above structure and determine the number of valence electrons is used till now.

In the above structure, four single bonds are used and every single bond contains  2 electrons, hence, (4 × 2) = 8 valence electrons are used from 14 total available valence electrons for drawing the lewis structure of NH2OH.

∴ (14 – 8) = 6 valence electrons

So, we are left with 6 valence electrons more.

4. Complete the octet of the atoms

In this step, we have to complete the octet of all atoms starting from the outer atom first.

Now, in the case of NH2OH, hydrogen is the outer atom and it needs only 2 electrons to fulfill the octet since it has only 1s shell which can be filled maximum of 2 electrons.

The hydrogen atoms already completed their octet since they have 2 electrons(one single bond) in their valence shell.

Now, the oxygen and nitrogen both need 8-8 electrons in their valence shell to complete the octet. Looking at the 3rd step structure of NH2OH, we see that nitrogen atom is attached to the three bond pairs means 6 electrons.

Hence, the nitrogen already has 6 electrons in its valence shells means it needs only two more. An oxygen atom is attached to the two bond pair that means, it has 4 electrons in its valence shell, therefore, it needs 4 more electrons to complete the octet.

So, the nitrogen atom needs 2 electrons and the oxygen atom needs 4 electrons to complete their octet. And we have already 6 remaining valence electrons.

Therefore, put these remaining valence electrons over oxygen and nitrogen and complete their octet shell.

NH2OH lewis structure

NH2OH lewis structure

That’s all, all the atoms in the above NH2OH lewis structure fulfilled their octet and attains stability and we also used all the total valence electrons that are available for drawing it.

Now we will check the above structure stability by evaluating the formal charge for each atom.

5. Check the stability with the help of a formal charge concept

To calculate the formal charge on an atom. Use the formula given below-

⇒ Formal charge = (valence electrons – nonbonding electrons –  1/2 bonding electrons)

The nonbonding electrons are basically lone pair electrons and bonding electrons are shared electrons that are found in between the atoms.

Let’s calculate the formal charge for nitrogen, oxygen, and hydrogen atoms in the NH2OH lewis structure.

For nitrogen atom:

⇒ Valence electrons of nitrogen = 5

⇒ Nonbonding electrons on nitrogen= 2

⇒ Bonding electrons around nitrogen(3 single bond) = 6

∴ (5 – 2 – 6/2) = 0 formal charge on nitrogen central atom.

 For hydrogen atom

⇒ Valence electrons of hydrogen = 1

⇒ Nonbonding electrons on hydrogen = 0

⇒ Bonding electrons around hydrogen (1 single bond) = 2

∴ (1 – 0 – 2/2) = 0 formal charge on the hydrogen atom.

 For oxygen atom

⇒ Valence electrons of oxygen = 6

⇒ Nonbonding electrons on oxygen =4

⇒ Bonding electrons around oxygen (2 single bonds) = 4

∴ (6 – 4 – 4/2) = 0 formal charge on the oxygen atom.

formal charge in NH2OH or H3NO lewis structure

So, all-atom in the above structure gets a formal charge equal to zero, hence, this is our most stable and appropriate lewis structure of NH2OH or H3NO.

What is the bond angle and molecular geometry of NH2OH?

The molecular geometry of NH2OH is Trigonal pyramidal and its electron geometry is tetrahedral since the central atom nitrogen has 4 electrons pairs around it(3 bond pair + 1 lone pair) which makes it an AX3N type molecule.

NH2OH molecular geometry or shape

The bond angle of NH2OH is followed as ∠H-N-H = 107º, ∠H-N-O = 103.3º, and ∠N-O-H = 101.4º.

NH2OH bond angle

FAQ

How many bond pairs and lone pairs are present in the lewis structure of NH2OH?

Bonding pairs are the pair of electrons that are in a bond. A single bond has one bond pair means 2 bonding electrons. 

Lone pairs are those represented as dots in the lewis diagram that do not take part in the formation of bonds and are also called nonbonding electrons.

So, in the NH2OH lewis structure, there are 4 bond pairs means 8 bonding electrons and 3 lone pairs (1 on central atom + 2 on oxygen atom) are present.

Why the electron geometry of NH2OH is tetrahedral?

The electron geometry considers both bond pair and lone pair while predicting the geometry of the molecule. And the molecular geometry only considers the bond pair to predict the shape of the molecule.

So, as per the NH2OH lewis structure, the nitrogen central atom is surrounded by 4 electron pairs(3 bond pairs + 1 lone pair).

∴ Four regions of electron density always form a tetrahedral geometry, hence, the electron geometry of NH2OH is tetrahedral.

Properties and uses of Hydroxylamine

  • Its molar mass is 33.030 g·mol−1 and its density is 1.21 g cm−3.
  • It forms trigonal coordination geometry at N.
  • Its boiling point is 58 °C and its melting point is 33 °C.
  • It acts as an antioxidant, as the nucleophilic reagent, and, as a reducing agent.
  • It has the power to hold the water and that’s why it is a hygroscopic compound.
  • It is used as an agent in conversion from cyclohexanone to caprolactam.
  • Hydroxylamine is explosive and can explode on heating.
  • The long term exposure to this can cause irritation in the skin, eyes, and in other organs. 

Preparation and reactions of Hydroxylamine

Hydroxylamine is prepared by electrolytic reduction of nitric acid with 3 moles of H2.

HNO3 + 3H2 → NH2OH + 2H2O

Hydroxylamine is prepared by the neutralization of Hydroxylammonium salts.

⇒ (NH3OH)Cl + NaOBu → NH2OH + NaCl + BuOH

Hydroxylamine can explode with heat.

⇒ 4NH2OH + O2 → 2N2 + 6H2O

In reaction with aldehyde or ketone, NH2OH produces oxime.

⇒ R2C=O + NH2OH∙HCl , NaOH → R2C=NOH + NaCl + H2O

Summary

  • The total valence electron is available for drawing the NH2OH Lewis structure is 14.
  • The molecular geometry or shape of NH2OH is trigonal pyramidal at N.
  • The lewis structure of NH2OH or H3NO has 8 bonding electrons and 6 nonbonding electrons.
  • NH2OH is polar in nature.
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