It is said that covalent bonds are directional, while ionic bonds are not. Why? Is it because of the orientation/directional properties of the overlapping orbitals?
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asked Jul 30, 2015 at 17:15
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3 Answers
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The meaning of covalent bonds being directional is that atoms bonded covalently prefer specific orientations in space relative to one another. As a result, molecules in which atoms are bonded covalently have definite shapes.
The reason for this directionality is that covalent bonds are formed by sharing electrons between atoms, or, in other words, as you said, by overlapping the atomic orbitals of participant atoms. And usually only few patterns of overlap are possible, consequently, only few spatial arrangements of atoms are possible.
Ionic bonds are different: there is no electron sharing (or atomic orbital overlaps) and the number of anions surrounding a cation is limited by the charges of the ions, their sizes, and the efficiency of the lattice packing.
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Very well put. Another explanation is that as covalent bonds are made by 'sharing' of electron, the electron will 'spend' more time with the element which is more electronegative. e.g in HCl, H has the electronegativity of 2.1 while Cl has 3, so the 'pull' of Cl on the shared electron is greater than H, hence the direction. Hence covalent bonds show directionality because of the shape of their electron wavefunction. Its the probability of finding an electron in a certain direction which is in turn effected by the partial charges. Even Ionic bonds show directionality (because there is no 'true' ionic' bond) but its very slight.
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9$\begingroup$ But there are non-polar covalent bonds too. Those are just as directional as the polar ones are. $\endgroup$ Commented Jul 31, 2015 at 8:59
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3$\begingroup$ Following on from orthocresol's point, I think you are confusing directionality with polarity. $\endgroup$– bonCommented Jul 31, 2015 at 12:46
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6$\begingroup$ Everyone! Technical inaccuracy != VLQ answer. You're trying to get this deleted, but in this case, as it isn't spam or link-only or comment-y, it doesn't need moderation, just vote about the quality, and the OP can decide whether they wanna delete it or not. || @Muzammil your comment makes better sense, but it's hardly simpler and easier. You might edit it into the answer though. $\endgroup$– M.A.R.Commented Jul 31, 2015 at 18:53
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In covalent bond mutually sharing present between more or less electronegative element. Eg; if we consider two elements A and B.electronegative of A is more than B.then electron density more on A and less on B. As a result B easily lose electron means that their is direction of losing electron and it's direction depends upon electronegative of element hence covalent bond is directional bond
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6$\begingroup$ -1 Look at the comments on the other answers... "But there are non-polar covalent bonds too. Those are just as directional as the polar ones are." Example: C-C bond in ethane. $\endgroup$ Commented Jan 7, 2016 at 4:28
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$\begingroup$ Welcome to Chemistry.SE! Take the tour to get familiar with this site. Mathematical expressions and equations can be formatted using $\LaTeX$ syntax. For more information in general have a look at the help center. At the moment this reads more like a comment than an actual answer - could you elaborate a little more. With a bit more rep, you will be able to post comments on any question/answer. $\endgroup$– Martin - マーチン ♦Commented Jan 7, 2016 at 10:42