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Two hydrogen atoms approach each other and form a bond. What fixes the bond length?
AThe separation of highest kinetic energy
BThe separation where repulsion is zero
CThe separation where orbitals first touch
DThe separation of lowest potential energy
Answer & Solution
Correct answer: D. The separation of lowest potential energy
1. As the atoms move closer, each shared electron is pulled by both nuclei and the energy falls.
2. Push them closer still and the two positive nuclei begin to repel, so the energy climbs again.
3. Between those two effects the potential energy passes through a minimum.
4. The internuclear distance at that minimum is the bond length.
5. Repulsion never falls to zero at any finite separation, so that option describes nothing real.
_Source: OpenStax Chemistry (CC BY 4.0), Chs 7 and 17, section 7.2 Covalent Bonding_
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