AQA A Level Chemistry

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p170027
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How do you know when a compound has a more covalent character please?
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TypicalNerd
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(Original post by p170027)
How do you know when a compound has a more covalent character please?
There are several ways of knowing.

One way is to compare the theoretical and experimental lattice enthalpies. If the theoretical lattice enthalpy has a smaller magnitude than the experimental lattice enthalpy, it’s because the bonding is stronger due to it having covalent character.

Another is to consider the difference in electronegativity between the elements making up the compound. The greater the difference, the more ionic the character of the bonding is.
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charco
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(Original post by TypicalNerd)
There are several ways of knowing.

One way is to compare the theoretical and experimental lattice enthalpies. If the theoretical lattice enthalpy has a smaller magnitude than the experimental lattice enthalpy, it’s because the bonding is stronger due to it having covalent character.

Another is to consider the difference in electronegativity between the elements making up the compound. The greater the difference, the more ionic the character of the bonding is.
This is incorrect.

Stronger bonding = greater lattice enthalpy
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TypicalNerd
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(Original post by charco)
This is incorrect.

Stronger bonding = greater lattice enthalpy
Are you sure you have understood my previous answer?

What I was trying to say was that if the theoretical value has a smaller magnitude (i.e is less exothermic), compared to the experimental (actual) value, the bonding is stronger than predicted. Or alternatively, it could be phrased as 'if the experimental (actual) value has a greater magnitude than the theoretical value, the bonding is stronger'.

I apologise if my poor phrasing made the answer less understandable, though it does actually look as though we actually agree on the lattermost of your two statements.

We could also be looking at it from different angles, as I have always worked with the lattice enthalpy of formation, as opposed to the lattice enthalpy of dissociation. The more negative (i.e the smaller) the lattice enthalpy of formation is, the stronger the bonding is.
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charco
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(Original post by TypicalNerd)
Are you sure you have understood my previous answer?

What I was trying to say was that if the theoretical value has a smaller magnitude (i.e is less exothermic), compared to the experimental (actual) value, the bonding is stronger than predicted. Or alternatively, it could be phrased as 'if the experimental (actual) value has a greater magnitude than the theoretical value, the bonding is stronger'.

I apologise if my poor phrasing made the answer less understandable, though it does actually look as though we actually agree on the lattermost of your two statements.

We could also be looking at it from different angles, as I have always worked with the lattice enthalpy of formation, as opposed to the lattice enthalpy of dissociation. The more negative (i.e the smaller) the lattice enthalpy of formation is, the stronger the bonding is.
I can see what you were trying to say, that if the magnitude of the experimental lattice enthalpy is greater than that of the theoretical, then there is likely to be some covalent character in the bonding.

Be careful using terms like "smaller" to mean more negative. You were better off sticking to magnitude as the negative value is indicative of the direction of enthalpy change not a number less than zero.
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