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Why is BF3 covalent while AlF3 is ionic?
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+ Physical chemistry
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Ludwig Nijholt
Why is BF3 covalent while AlF3 is ionic?
Both Boron (B) and Aluminium (Al) belong to same group, so their valences are same. But Boron is exceptionally very samll, which makes it much more electronegative. As a result of it when it chemically reacts with other elements, the atoms of Boron don't loose electrons easily, rather keep them in sharing. So we have BF3 covalent compound and AlF3 as ionic.
Both Boron (B) and Aluminium (Al) belong to same group, so their valences are same. But Boron is exceptionally very samll, which makes it much more electronegative. As a result of it when it chemically reacts with other elements, the atoms of Boron don't loose electrons easily, rather keep them in sharing. So we have BF3 covalent compound and AlF3 as ionic.
In the gaseous state, the two are very similar, forming discrete molecules, much as so-called “covalent” molecules would. The difference is the energy needed to get them into the gaseous state. BF3 is gaseous at room temperature, with a low boiling point. AlF3 at room temperature is a network solid with a high temperature needed to form AlF3 molecules.
Because fluorine has such a high electronegativity, the bonds of the other elements with fluorine tend to be highly polar. Al-F bonds have 75% ionic character while B-F bonds have 61% ionic character. Both kinds of bonds are highly polar. The difference in the two is not so much “ionic” vs “covalent”, but rather the type of structure with the lowest energy, discrete molecule vs network solid, that makes the difference.
In the gaseous state, the two are very similar, forming discrete molecules, much as so-called “covalent” molecules would. The difference is the energy needed to get them into the gaseous state. BF3 is gaseous at room temperature, with a low boiling point. AlF3 at room temperature is a network solid with a high temperature needed to form AlF3 molecules.
Because fluorine has such a high electronegativity, the bonds of the other elements with fluorine tend to be highly polar. Al-F bonds have 75% ionic character while B-F bonds have 61% ionic character. Both kinds of bonds are highly polar. The difference in the two is not so much “ionic” vs “covalent”, but rather the type of structure with the lowest energy, discrete molecule vs network solid, that makes the difference.
Both Boron (B) and Aluminium (Al) belong to same group, so their valences are same. But Boron is exceptionally very samll, which makes it much more electronegative. As a result of it when it chemically reacts with other elements, the atoms of Boron don't loose electrons easily, rather keep them in sharing. So we have BF3 covalent compound and AlF3 as ionic.
Both Boron (B) and Aluminium (Al) belong to same group, so their valences are same. But Boron is exceptionally very samll, which makes it much more electronegative. As a result of it when it chemically reacts with other elements, the atoms of Boron don't loose electrons easily, rather keep them in sharing. So we have BF3 covalent compound and AlF3 as ionic.
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BF3 vs AlF3 …..
In the gaseous state, the two are very similar, forming discrete molecules, much as so-called “covalent” molecules would. The difference is the energy needed to get them into the gaseous state. BF3 is gaseous at room temperature, with a low boiling point. AlF3 at room temperature is a network solid with a high temperature needed to form AlF3 molecules.
Because fluorine has such a high electronegativity, the bonds of the other elements with fluorine tend to be highly polar. Al-F bonds have 75% ionic character while B-F bonds have 61% ionic character. Both kinds of bonds are highly polar. The difference in the two is not so much “ionic” vs “covalent”, but rather the type of structure with the lowest energy, discrete molecule vs network solid, that makes the difference.
BF3 vs AlF3 …..
In the gaseous state, the two are very similar, forming discrete molecules, much as so-called “covalent” molecules would. The difference is the energy needed to get them into the gaseous state. BF3 is gaseous at room temperature, with a low boiling point. AlF3 at room temperature is a network solid with a high temperature needed to form AlF3 molecules.
Because fluorine has such a high electronegativity, the bonds of the other elements with fluorine tend to be highly polar. Al-F bonds have 75% ionic character while B-F bonds have 61% ionic character. Both kinds of bonds are highly polar. The difference in the two is not so much “ionic” vs “covalent”, but rather the type of structure with the lowest energy, discrete molecule vs network solid, that makes the difference.
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