Water is the source of life on earth. Our life is primarily connected with it. Every life-giving process in our body occurs due to it.
A six-fold or four-fold geometry makes up the foundation for the structure of space-time. And this geometry of water structure conforms to this geometry of space-time. That’s why all life emerges from the water.
In this article, we will see what is the Lewis structure of a water molecule and what does it say about the water molecule?
Lewis Structure of Water
Table of Contents
Lewis structure is also called electron dot structure. It is a way of representing the valence electrons by dots surrounding the central atom.
In the Lewis structure of water, there are two single bonds around the oxygen atom. The two hydrogen atoms are attached to this oxygen through these bonds. Furthermore, oxygen has two lone pairs. The above structure is drawn using valence electrons of oxygen and hydrogen atoms.
|Sr No||Name of molecule||Water|
|2||Molecular geometry||Distorted tetrahedral geometry|
|3||No. of valence electrons||8|
General Rules to Draw a Lewis Structure
While drawing a Lewis structure, we have to follow some steps. The steps are given below
- Determine the total no. of valence electrons
- Determine total lone pair electrons and bond pair electrons
- Select the central atom
- Indicate lone pairs on atoms
- Indicate charges on atoms(if present)
- Convert lone pairs to bond pairs to minimize the charges and to check the stability
6 Steps to draw Lewis Structure of Water
Step 1: Determine the Total no. of Valence Electrons
In H2O, there are two elements; one is hydrogen and the other is oxygen. Let’s find the no. of valence electrons in a molecule of water
By hydrogen atoms
Valence electrons = 1 × 2 = 2
By oxygen atoms
Valence electrons = 6 × 1 = 6
Total no. of valence electrons = 2 + 6 = 8
Step 2: Determine the Total Lone Pair and Bond Pair of Electrons
We calculate the total electron pairs by dividing total valence electrons by two. For water, the total pair of electrons in its valence shell is 4.
Step 3: Select the Central Atom
The atom with a high valence can keep the central position. So, from hydrogen and oxygen which will be the center atom? The valence of oxygen is two while hydrogen has one. Oxygen has higher valence so it is the central atom. This is how we can show the location of atoms in the molecule.
H — O — H
Step 4: Indicate the Lone Pairs on Atoms
It’s we have selected the central atom and have a sketch of the water molecule. After that, we have to indicate the lone pair of electrons.
We have four electron pairs. Two H-O bonds have already been drawn in the Lewis structure. Now only two electron pairs are remaining to indicate.
Usually, we mark the remaining electron pairs on outside atoms. But in H2O, hydrogen atoms which are the outer atoms cannot keep more than two electrons in their valence shell.
We have to mark those two electron pairs on the central atom, oxygen.
Step 5: Indicate Charges on Atoms
There are no charges on oxygen and hydrogen atoms.
Step 6: Reducing the Charges on Atoms and Checking the Stability
A structure having many charges is not stable. If we get such a structure, we should try to reduce the charges by converting the lone pairs to bonds.
As there is no charge on atoms so we have already got the best Lewis structure for water.
Molecular Geometry of Water
The bond angle among oxygen-hydrogen-oxygen atoms is 104.5.˚However, this confirms that the geometrical structure of a water molecule is bent.
Valence Shell Electron Pair Repulsion (VSEPR) theory, explains why the bond angle is reduced to 104.5 irrespective of two lone pairs of electrons on the oxygen atom. The ideal bond angle for a bent-shaped molecule is 109.5. The lone pair of electrons twisted the bond angle.
Hybridization of Water Molecule
Only a sigma bond is present between each oxygen-hydrogen bond. The strength of the sigma bond makes the oxygen-hydrogen bond stable.
According to the rule, only the center atom undergoes hybridization. In H2O hybridization, the oxygen atom is sp3 hybridized.
The center atom, oxygen is hybridized. As the single oxygen atom has one 2s orbital and three 2p orbitals. These four orbitals form four sp3 hybridized orbitals that create a tetrahedral bent.
Why Water Molecule is Polar?
Water is a polar molecule. When we say that a molecule is polar, we mean that the charges are not evenly distributed in the structure. Here we will see which factors make the water molecule polar.
- Due to different electronegativity values of oxygen and hydrogen
- Lone pair of electrons on oxygen cause repulsion to lone-pair and bond-pair electrons
- The positive charge on one side, oxygen, and a negative charge on another side, hydrogen
What Does The Structure Of Water Say About Its Molecule?
The polar nature of water gives it unique properties. Here is an overview of those.
Excellent solvent- ability to dissolve many polar molecules and ions
High heat capacity- Requires a lot of energy to raise the temperature so the temperature is relatively constant
The high heat of vaporization- Requires much heat to change into vapors
Cohesive and adhesive properties- Shows strong cohesive and adhesive properties due to its ability to form hydrogen bonds
- Water is a liquid at STP (standard temperature and pressure)
- It is tasteless and odorless
- It can add both acids and base
- The molar mass of water is 18g/mol.
Let’s summarize everything we have discussed in this article till now:
- There are two sigma bonds between oxygen-hydrogen atoms in the water molecules. Moreover, there are two lone pairs of electrons that make the tetrahedral bent geometry.
- The hybridization is sp3 because it has one s orbital from hydrogen and three p orbital from oxygen.
- The water molecule is bent-shaped. So, it has an unequal distribution of electrons over hydrogen and oxygen atoms. That’s why it is polar.
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Q1. What type of bond is H2O?
Water is formed by covalent bonding. In water, the atoms share their valence electrons.
Q2. Are water molecules polar?
There is an unequal sharing of electrons between the atoms in water. The unsymmetrical shape and formation of two poles; a positive charge on H and a negative charge on O make it a polar molecule.
Q3. What is special about the structure of water?
Water is a polar covalent bond but oxygen is more electronegative than hydrogen. So oxygen pulls the electrons and causes a partial positive charge on the hydrogen side and a partial negative charge on the oxygen side. It has a bent structure.
Q4. Why does H2O have a bent shape?
In H2O, two hydrogen atoms are bonded to an oxygen atom. But the oxygen atom also consists of two unshared electron pairs. This makes the structure bent.