In a water molecule, two hydrogen and one oxygen atom are held together by ________ bonds.

Question

BlackTom AI · Accepted Answer

Oxygen shares electrons with the two hydrogens to form covalent bonds.

Relevant concepts:
- Covalent bonds form when atoms share electron pairs to achieve full valence shells (octet for most, duet for H).
- Ionic bonds form by complete electron transfer producing oppositely charged ions.
- Hydrogen bonds and van der Waals forces are intermolecular attractions (between molecules), not the primary bonds holding atoms together within a single molecule.
- Electronegativity difference helps classify bond character: on the Pauling scale O ≈ 3.44 and H ≈ 2.20 (difference ≈ 1.24), indicating a polar covalent bond rather than full ionic character.

Step-by-step reasoning and intermediate steps:
1. Count valence electrons: oxygen has 6 valence electrons; each hydrogen has 1. To satisfy oxygen’s octet, it needs 2 additional electrons.
2. Each hydrogen can share its single electron with oxygen. By sharing, oxygen gains two electrons (one from each H) and each hydrogen attains a duet (2 electrons).
3. Lewis structure: H—O—H, with two single bonds representing two shared electron pairs (one pair between O and each H). This is the hallmark of covalent bonding.
4. Evaluate bond type via electronegativity: Δχ = 3.44 − 2.20 = 1.24. This moderate difference yields a polar covalent bond (electron density pulled toward oxygen) rather than a full ionic bond (which generally requires a much larger Δχ).
5. Note: Hydrogen bonding occurs between water molecules (the slightly positive H of one molecule is attracted to the slightly negative O of another), but these are intermolecular and not the bonds holding H and O together within the same molecule.

Why the correct answer is correct:
- The internal O–H connections result from shared electron pairs (covalent bonds), satisfying valence needs of H and O.
Why other options are incorrect:
- "Oxygen" is not a bond type.
- "Van der waals" and "hydrogen" refer to weaker intermolecular forces between molecules, not the intramolecular bonds in H2O.
- "Ionic" implies full electron transfer to form ions (O2− and H+), which does not describe the actual shared-electron arrangement in water.

Conclusion: The correct choice is covalent, consistent with the provided answer.

In a water molecule, two hydrogen and one oxygen atom are held together by ________ bonds.单项选择题

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