Compare the Lewis symbol for neon with the Lewis structure for methane, CH4. How many valence electrons are in each structure? How many bonding pairs and how many nonbonding pairs does each structure have?
The Correct Answer and Explanation is:
Correct Answer:
Neon (Ne):
- Valence electrons: 8
- Bonding pairs: 0
- Nonbonding pairs: 4
Methane (CH₄):
- Valence electrons: 8 (Carbon) + 1×4 (Hydrogen) = 12 total
- Bonding pairs: 4
- Nonbonding pairs: 0
The Lewis symbol and Lewis structure are tools used to represent the valence electrons of atoms and molecules, respectively. These representations help predict bonding behavior and molecular structure.
Neon (Ne) is a noble gas found in Group 18 of the periodic table. Its Lewis symbol is represented as the chemical symbol “Ne” surrounded by 8 dots, each dot symbolizing a valence electron. Neon has a complete octet, meaning it already has 8 valence electrons and is chemically stable. Therefore, it does not typically form bonds with other atoms. All four electron pairs are nonbonding pairs, or lone pairs, as there are no shared electrons in bonds. This inertness is a hallmark of noble gases.
In contrast, methane (CH₄) is a simple molecule consisting of one carbon atom and four hydrogen atoms. Carbon has 4 valence electrons, while each hydrogen has 1 valence electron. To achieve a full octet for carbon and a duet for each hydrogen, carbon forms four single covalent bonds with the four hydrogen atoms. Each bond involves a pair of shared electrons, one from carbon and one from hydrogen, forming 4 bonding pairs. There are no nonbonding pairs in methane’s Lewis structure, as all of carbon’s valence electrons are used in bonding, and hydrogen atoms do not carry lone pairs in stable molecules.
Thus, the Lewis symbol for neon emphasizes its lack of chemical reactivity with 8 nonbonding electrons, while the Lewis structure for methane shows a tetrahedral bonding arrangement with 4 bonding pairs and no lone pairs. This comparison highlights how the number and arrangement of valence electrons determine an element’s or molecule’s bonding behavior and chemical properties.
