The total number of nonbonding electron pairs present in the Lewis structure of CH4 is

Question

BlackTom AI · Accepted Answer

Carbon has four valence electrons and in CH4 it forms four single C–H bonds, using all four electrons in bonding so there are no lone (nonbonding) electron pairs.

1. Relevant knowledge points and concepts
- Valence electrons: the electrons available for bonding (C = 4, H = 1 each).
- Lewis structure rules: place atoms, connect with single bonds, distribute remaining electrons as lone pairs to satisfy octet/duet rules.
- A nonbonding electron pair (lone pair) is a pair of valence electrons that is not shared in a covalent bond. Bonding pairs (shared electrons) are not counted as nonbonding.

2. Step-by-step reasoning
- Step 1: Count total valence electrons.
  - Carbon: 4
  - Four hydrogens: 4 × 1 = 4
  - Total = 4 + 4 = 8 valence electrons.
- Step 2: Draw a skeleton with C central and four H atoms each bonded to C.
- Step 3: Assign electrons to bonds. Each C–H single bond uses 2 electrons.
  - Four C–H bonds use 4 × 2 = 8 electrons.
- Step 4: Subtract electrons used in bonds from total valence electrons.
  - 8 total − 8 used = 0 electrons remaining to place as lone pairs.
- Step 5: Check octet/duet: Carbon has 8 electrons around it (four bonds), each H has 2 electrons (one bond). All atoms satisfied.

3. Intermediate calculations shown
- Total valence e− = 4 (C) + 4 × 1 (H) = 8 e−
- Electrons in bonds = 4 bonds × 2 e−/bond = 8 e−
- Remaining e− for lone pairs = 8 − 8 = 0 e− → 0 lone pairs → 0 nonbonding pairs

4. Why the correct answer is correct
Because all valence electrons are used to form the four C–H bonding pairs, there are no leftover electron pairs to be nonbonding. Thus the number of nonbonding electron pairs is zero.

5. Why other options are incorrect
- Any nonzero option (one, two, three, four) would imply leftover electrons not used in bonding; that contradicts the electron count and would leave fewer than four C–H bonds (violating carbon’s tetravalence) or break the octet/duet rules.

6. Conclusion
The total number of nonbonding electron pairs in the Lewis structure of CH4 is zero. This matches the provided answer: zero.

The total number of nonbonding electron pairs present in the Lewis structure of CH4 is单项选择题

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