N2O Lewis Structure, Resonance Structures, Oxidation Number
N2O (nitrous oxide) is an oxide of nitrogen and is called as laughing gas. In this tutorial, we are going to learn followings of nitrous oxide gas.
- How to draw the lewis structure for N2O
- Drawing resonance structures following the lewis structure
- Oxidation numbers of nitrogen and oxygen atoms.
If you already know the lewis structure of N2O, you can skip first section of this tutorial and can go to the lewis structure part directly.
Lewis structure of N2O
There are several steps to follow in drawing the lewis structure of N2O. aAl of them are explained in detail in this tutorial and a beginner can learn basics of drawing lewis structure.
Number of electrons of valance shell
First, we should know, how many electrons of valence shells of oxygen and nitrogen atoms will be supplied to form the molecule.
Number of electrons in the valence shell of nitrogen atom = 5
Number of nitrogen atoms in the N2O molecule = 2
Number of electrons given by nitrogen atoms = 5*2 = 10
Number of electrons in the valence shell of oxygen atom = 6
Total electrons given by the all atoms = 10 + 6 = 16
Number of total electrons repulsing pairs (sum of σ + π + lone pairs in valance shells) = 16/2 = 8
Center atom of N2O
Usually nitrogen atom has the the greatest possibility of being the center atom than oxygen atom because nitrogen can show high valance than oxygen.
So one of the nitrogen atom is located as the center atom and other atoms are located around it. Now we can imagine a sketch for N2O and it is figured below.
Charges on atoms
When a molecule is being drawn, we should be careful always to minimize the charges on atoms because when charges of atoms are low, stability of that molecule is great.
Structure 1
Look the structure 1, there are positive and charges on every atoms in the N2O molecule. So this structure does not seem as a stable structure. Therefore we should try to draw another structure by changing the structure 1.
Make a new bond by converting a lone pair in the nitrogen atom in the side (not in the center nitrogen atom).
Structure 2
A long pair in the nitrogen atom (left side) is now caused to form a bond between nitrogen atoms. So now there is a double bond between nitrogen atoms. With that, density of charges on atoms are decreased.
But, you can see, there are charges still on atoms. So let's try another structure for N2O to lower the charges if its possible.
Structure 3
Another long pair in the nitrogen atom (left side) is now caused to form a bond between nitrogen atoms. So now there is a triple bond between nitrogen atoms.
In this structure, charges on atoms are decreased furthermore. Now center nitrogen atom has only +1 charge and oxygen atom has a -1 charge.
Structure 3 is the best (most stable) structure we can draw for N2O. It's center atom contains, around it,
- two sigma (σ) bonds
- zero lone pairs
Shape of N2O molecule around center atom
N2O molecule contains two nitrogen atoms and one oxygen atoms. First we should try to draw the most stable lewis structure of N2O to decide the shape of N2O molecule.
Number of lone pairs and number of σ bonds around the center atom are important for finding the shape of a molecule.
Due to two sigma bonds and zero lone pairs around center atom (nitrogen), shape of N2O molecule is linear.
We can draw N2O resonance structures to identify the most stable structure of N2O. Oxidation numbers of nitrogen in N2O is decided from most stable structures. Finally we build the shape of N2O molecule.
N2O resonance structures
Electronegativity of oxygen is higher than nitrogen. This means a negative charge on oxygen atom is more stable than a negative charge on nitrogen atom. Otherwise we can say, oxygen likes electrons more than nitrogen.
Structure 3 is the most unstable resonance of N2O because there is a positive charge on oxygen atom.
Structure 2 has some stability.
Structure 1 is the most stable resonance because oxygen holds the negative charge.
Oxidation states, numbers of N2O
We can calculate oxidation states of N2O for most stable resonance structure.
Oxidation state of N2O
Oxidation number of nitrogen in N2O is +1. But in real situation, one nitrogen atom is at +2 oxidation state and other nitrogen atom is at 0 oxidation state. Oxidation number of oxygen is -2.
Oxidation number from equation
We know in most occasions, oxidation umber of oxygen is -2. There are two nitrogen atoms in N2O. Take oxidation number of nitrogen is x. Overall charge of N2O molecule is 0.
Some of oxidation numbers of each element in the molecule should equal to the zero.
x*2 + (-2) = 0
x = +1
is N2O molecule linear in structure?
yes. N2O molecule has a linear shape.
Which will be the central atom in n2o and what will be its charge?
Nitrogen's valence is higher than oxygen. So, as the central atom, nitrogen atom is selected. Charge of nitrogen atom is +1 in N2O molecule..
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