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It is insufficient to simply state that fluorine is more electronegative than bromine. You must state why, which is because there's less shielding as fluorine has less energy levels.
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It's referring to the availability of the lone pair of electrons on fluorine. A hydrogen bond needs to things; a hydrogen atom with a high delta charge, and a lone pair of electrons to attract the hydrogen atom. The lone pair of electrons is more dense at the 2nd energy level. In higher energy levels, (Bromine is period 4), the electron pair is more diffuse and so there is a lower charge density. Thus it's less likely to attract a positive charge.
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It is insufficient to simply state that fluorine is more electronegative than bromine. You must state why, which is because there's less shielding as fluorine has less energy levels.
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It's referring to the availability of the lone pair of electrons on fluorine. A hydrogen bond needs to things; a hydrogen atom with a high delta charge, and a lone pair of electrons to attract the hydrogen atom. The lone pair of electrons is more dense at the 2nd energy level. In higher energy levels, (Bromine is period 4), the electron pair is more diffuse and so there is a lower charge density. Thus it's less likely to attract a positive charge.
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Bromine is a larger atom. This increased distance between the nucleus and outer electrons weakens the electrostatic force of attraction so the electron cloud is more loosely bound. It's more free to disperse.
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There are more energy levels and so increased shielding further weakening the electrostatic force of attraction. (These first two points are pretty much interlinked, but my exam board treated them as two separate points)
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The outer energy energy level is larger in diameter so the orbitals will be much large. Since each orbital only contains two electrons/two negative charges, the distribution of this negative charge will be much greater.
Spoiler
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Bromine is a larger atom. This increased distance between the nucleus and outer electrons weakens the electrostatic force of attraction so the electron cloud is more loosely bound. It's more free to disperse.
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There are more energy levels and so increased shielding further weakening the electrostatic force of attraction. (These first two points are pretty much interlinked, but my exam board treated them as two separate points)
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The outer energy energy level is larger in diameter so the orbitals will be much large. Since each orbital only contains two electrons/two negative charges, the distribution of this negative charge will be much greater.
Spoiler