✔ 最佳答案
The bond enthalpy of F‑F bond is lower than expected. This is because of the anomalously strong repulsion between the unshared pairs of electrons as F atoms are very small. Note that the repulsion is between the unshared pairs of electrons on one F atom to the unshared pairs of electrons on another F atom.
In HF, there is no such anomalously strong repulsion between H and F atoms, because H atom does not have unshared pair of electrons.
2007-03-20 11:34:27 補充:
Charge density is a quantity to describe the distribution of charge on an ion (esp. a cation).Charge density = (Charge carried by the ion) / (Ionic volume)Charge density is NOT applied to atoms (e.g. H atom) or molecules (e.g. F2 molecule).