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How to draw the Lewis structure of methane, CH4
By José @ Periodic table with names
http://periodictablewithnames.net
Steps to write the Lewis structure of methane
1. Find the number of valence electrons for each of the atoms in the molecule.
The number of valence electrons is usually the same as the group number where the element is located.
The number of valence electrons for hydrogen is 1 (group 1)
The number of valence electrons for carbon is 4 (group 4)
• Methane: CH4
• C is located in group 4, thus possess 4 valence electrons
• H is located in group 1, thus possess 1 valence electron
2. Count the total number of valence electrons in the molecule:
Sum the valence electrons from each atom in the molecule
For methane CH4
• Total valence e. from C: 44 e. x 1 C = 4
• Total valence e. from H: 41 e. x 4H = 4
Total valence e. in the molecule: 4 + 4 = 8
3. Use the octet rule to figure how many octet electrons the atoms should have:
Most atoms need 8 electrons to complete their valence shield
Hydrogen is an exception and needs only 2
For methane CH4
• Carbon should have 8 valence electrons
• Each hydrogen should have 2 valence electrons
4. Draw an initial sketch of the molecule by placing the symbol of each atom in a diagram
For methane:H
H C HH
5. Place the valence electrons of each atom around them, starting from the outer atoms
For methane CH4
• Hydrogen has 1 valence electron:
C
H
H
H
H
For methane CH4
• Carbon has 4 valence electrons:
C
H
H
H
H
6. Each bond in a molecule is made up from two electrons.
Each atom in the molecule need to be bonded together to its nearest atom.
For methane CH4
• Form single bonds between the atoms:
C
H
H
H
H
C
H
H
H
H
For methane CH4
• Form single bonds between the atoms:
C
H
H
H
H
For methane CH4
• Form single bonds between the atoms:
For methane CH4
• Form single bonds between the atoms:
C
H
H
H
H
For methane CH4
Now the structure is complete:
C
H
H
H
H
7. At the end, each atom should be surrounded by eight electrons (following the octet rule)
Remember that H only needs 2 electrons
For methane CH4
• Carbon is surrounded by 8 electrons
C
H
H
H
H
For methane CH4
• Each hydrogen is surrounded by 2 electrons
C
H
H
H
H
Practice writing the Lewis structure of any molecule!
For more resources on chemistry visit:Periodic table with names
http://periodictablewithnames.net