Answer:
The logic behind drawing Lewis formulas is to use the valence electrons of the elements and complete the Octet rule.
Explanation:
The logic behind drawing Lewis formulas is to use the valence electrons of the elements and complete the Octet rule.
Valence electrons are the electrons of an atom that are located in the last shell. We represent the valence electrons using dots between covalent bonds.
The Octet rule says that an element loses or gains electrons in order to achieve the electron configuration of the nearest noble gas, it means that it will try to have 8 electrons in the last shell.
For example: CH3OCH3
1st) It is necessary to find the total number of valence electrons. We can find the electrons of valence of each atom in the Periodic Table, and then we have to multiply it by the number of atoms in the molecule:
- Total number of valence electrons of C: 4e * 2 = 8e
- Total number of valence electrons of H: 1e * 6 = 6e
- Total number of valence electrons of O: 6e * 1 = 6e
Total number of valence electrons of CH3OCH3 = 20e (8 + 6 + 6 = 20)
2nd) Now we have to start drawing with the least electronegative atom in the center. In this case, we have to draw the O in the center (even though it is not the least electronegative atom in the molecule), because it is the only one that has only 1 atom in this molecule, and hydrogen atoms always go on the outside:
We have to start drawing the electrons, trying to complete the octets on the outside atoms, in this case, hydrogen, then carbon, and finally oxygen.
Hydrogen atom only needs 2 valence electrons to complete the last sheel.
