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Lewis Structure of NO3- (Nitrate ion)

Lewis Structure of NO3- (Nitrite ion)


chemistry homework assignment help for students

Lewis structure of NO3- ion is drawn step by step in this tutorial. Total valence electrons of nitrogen and oxygen atoms and negative charge are considered to draw the NO3- lewis structure. You will every fact of drawing lewis structures from this tutorial which will help you to draw more lewis structures in the future.



Lewis Structure of nitrite ion

lewis structure of NO3-

Now, we are going to learn, how to draw this lewis structure of NO3- ion.



Steps of drawing NO3- lewis structure

Following steps are required to draw NO3- lewis structure and they are explained in detail in this tutorial.


  1. Find total number of electrons of the valance shells of nitrogen and oxygen atoms and including charge of the anion
  2. Total electrons pairs in valence shells
  3. Center atom selection from nitrogen and oxygen atom
  4. Put lone pairs on atoms
  5. Stability of lewis structure - Check the stability and minimize charges on atoms by converting lone pairs to bonds.

Drawing correct lewis structure is important to draw resonance structures. In another tutorial, we learn how to draw resonance structures of nitrate ion.



Total number of electrons of the valance shells of nitrogen and oxygen atoms and charge of the anion

There are one nitrogen atom and three oxygen atoms in the nitrate ion. Also there is a -1 charge on the nitrate ion.

Nitrogen and oxygen are located at VA and VIA groups respectively in the periodic table. So nitrogen has five electrons in its valence shell. In oxygen atom, there are six electrons in its valence shell.


  • Total valence electrons given by nitrogen atom = 5

There are three oxygen atoms in NO3-, Therefore

  • Total valence electrons given by oxygen atoms = 6 *3 = 18

Due to -1 charge, another electrons is added

  • Due to -1 charge, received electrons to valence electrons= 1

  • Total valence electrons = 5 + 18 + 1 = 24


Total valence electrons pairs

Total valance electrons pairs = σ bonds + π bonds + lone pairs at valence shells

Total electron pairs are determined by dividing the number total valence electrons by two. For, NO2-, there are 24 valence electrons, so total pairs of electrons are 12.



Center atom of NO2-

To be the center atom, ability of having greater valance is important. Nitrogen can show valence,5. But, oxygen's maximum valence is 2. Therefore nitrogen has the more chance to be the center atom (See the figure). So, now we can build a sketch of NO3- ion.


Sketch of NO2- ion

center atom of NO3-

Lone pairs on atoms

There are already three N-O bonds in the sketch. Therefore only nine valence electrons pairs are remaining to draw the rest of ion.

Start to mark those nine valence electrons pairs on outside atoms (oxygen atoms) as lone pairs. One oxygen atom will take three lone pairs following the octal rule (oxygen and nitrogen atoms cannot keep more than eight electrons in their valence shells). All nine valence electrons pairs (9) are spent when lone pairs are marked on oxygen atoms.

Therefore, there is no ine valence electrons pairs to mark on nitrogen atom.

valence electrons of lewis of NO3-.jpg


Check the stability of drawn NO2- ion and minimize charges on atoms by converting lone pairs to bonds

Check charges on atoms and mark them as below. Charges are important to decide the lewis structure of the ion.

steps of drawing lewis structure of NO3- ion

The drawn structure for NO3- is not a stable structure because oxygen atoms and nitrogen atoms have charges. When a molecule or ion has so many charges on atoms, that structure is not stable.


Now, we should try to minimize charges by converting lone pair or pairs which exist on oxygen atoms to bonds. So we convert one lone pair of one oxygen atom as a N-O bond.

mimimize charges of NO3- ion to draw lewis structure

Now there is a double bond between nitrogen and one oxygen atom. There are also two single bonds (N-O) with nitrogen atom and other oxygen atoms.

lewis structure of nitrate ion

In new structure, charges of atoms are reduced. Now there is no any charge on one oxygen atom. Also, charge of nitrogen atom is reduced from +2 to +1. Now you understand this structure of NO3- is more stable than previous structure due to less charges on atoms.


But, We cannot convert more lone pairs of other oxygen atom to make a bond with nitrogen atom because nitrogen cannot keep more than eight electrons in its last valence shell.




Questions


How many lone pairs are around the nitrogen atom in nitrate ion?

No electrons pairs exist on nitrogen atom. But, on nitrogen atom, there is a +1 charge. Around the nitrogen atom, there are two single bonds and double bond.



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