Ionic bonds are strong but not as strong as purely covalent network solids. And the problem is further complicate by definitions of strength that are too narrow. Are metals stronger or weaker than diamond-like structures?
It depends what you mean by strength. Diamond is harder than any metal but it is also more brittle. If resilience to being struck with a sharp object matters, choose a ductile metal object over a diamond any day. This happens because the crystal structure in some metals can absorb energy by reorganising crystal defects rather than by shattering bonds pretty much the only option in silica or diamond. So, in one sense, metals are stronger than covalent solids. The overall lesson is to be careful about definitions.
There is no good generalisation of crystal strength based on bond types. Be careful whether you are talking about the bonds within the components of the crystal molecules or the bonds that hold those components together many "covalent" compounds consist of crystals where molecules are held together by much weaker forces. Don't forget that many minerals have both ionic and covalent bonding.
And be specific about what you mean by "strength" eg harness are resilience to impact are not the same thing. Ionic and metallic bonds are weaker than covalent bonds. The second statement is wrong because firstly melting point is not proportional to the strength of chemical bond. There are more factors such as flexibility of molecules. Boiling point is more proportional instead. More important, the inter-particle forces to be compared among the organic compound vs ionic vs metallic compound is NOT among covalent bond vs ionic bond vs metallic bond.
It is among intermolecular force dipole-dipole, H-bond, Van der waals vs ionic bond vs metallic bond. And the first one is much weaker than the second and third for sure. So the boiling point of organic compounds is much lower. I am not sure what is the consensus that has been arrived at by chemists around the world but I would just like to offer my two cents' worth on the issue. This question has always been a question which my teachers would always tackle when they teach chemical bonding and their answer has always been the same:.
It is not fair to make a comparison since these bonds are ultimately very variable in terms of strength. The strength of covalent bonds in simple molecular substances as well as those in giant network structures can be easily determined.
Thus, the bond energies of most covalent bonds are known well and they can be easily used for such comparisons of bond energy. However, the strength of ionic bonds and metallic bonds is not so clear-cut.
By definition, the ionic bond is the electrostatic force of attraction between positively and negatively charged ions in an ionic lattice while the metallic bond is the electrostatic force of attraction between the positively charged metal ions and the surrounding electrons.
In an ionic lattice, there are so many ions interacting electrostatically with each other. How then can the strength of the ionic bond be determined?
The idea of lattice energy could be used but comparisons made using lattice energy would only be of any sense when we are comparing between ionic lattice. It cannot be used to compare with covalent bonds!
Both are in terms of "per mole of something". But that "something" is different in each case. The ionic bond strength is not so easily determined because each ion is in an electrostatic environment which is influenced by all the other ions around it. The same idea can be applied to metallic bonds. In essence, my take is that there is no basis of fair comparison between metallic, ionic and covalent bonds in terms of their bond strengths.
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Create a free Team What is Teams? This occurs because D values are the average of different bond strengths; therefore, they often give only rough agreement with other data. It has many uses in industry, and it is the alcohol contained in alcoholic beverages. It can be obtained by the fermentation of sugar or synthesized by the hydration of ethylene in the following reaction:. An ionic compound is stable because of the electrostatic attraction between its positive and negative ions.
The lattice energy of a compound is a measure of the strength of this attraction. For the ionic solid MX, the lattice energy is the enthalpy change of the process:.
Note that we are using the convention where the ionic solid is separated into ions, so our lattice energies will be endothermic positive values. Some texts use the equivalent but opposite convention, defining lattice energy as the energy released when separate ions combine to form a lattice and giving negative exothermic values.
Thus, if you are looking up lattice energies in another reference, be certain to check which definition is being used. In both cases, a larger magnitude for lattice energy indicates a more stable ionic compound. Thus, the lattice energy of an ionic crystal increases rapidly as the charges of the ions increase and the sizes of the ions decrease. When all other parameters are kept constant, doubling the charge of both the cation and anion quadruples the lattice energy.
Different interatomic distances produce different lattice energies. The compound Al 2 Se 3 is used in the fabrication of some semiconductor devices. Which has the larger lattice energy, Al 2 O 3 or Al 2 Se 3? The O 2— ion is smaller than the Se 2— ion. Thus, Al 2 O 3 would have a shorter interionic distance than Al 2 Se 3 , and Al 2 O 3 would have the larger lattice energy.
How would the lattice energy of ZnO compare to that of NaCl? ZnO would have the larger lattice energy because the Z values of both the cation and the anion in ZnO are greater, and the interionic distance of ZnO is smaller than that of NaCl. It is not possible to measure lattice energies directly. However, the lattice energy can be calculated using the equation given in the previous section or by using a thermochemical cycle.
Figure 1 diagrams the Born-Haber cycle for the formation of solid cesium fluoride. We begin with the elements in their most common states, Cs s and F 2 g. In the next step, we account for the energy required to break the F—F bond to produce fluorine atoms. Converting one mole of fluorine atoms into fluoride ions is an exothermic process, so this step gives off energy the electron affinity and is shown as decreasing along the y -axis. We now have one mole of Cs cations and one mole of F anions.
These ions combine to produce solid cesium fluoride. The enthalpy change in this step is the negative of the lattice energy, so it is also an exothermic quantity.
In this case, the overall change is exothermic. Table 5 shows this for cesium chloride, CsCl 2. Thus, the lattice energy can be calculated from other values. For cesium chloride, using this data, the lattice energy is:. The Born-Haber cycle may also be used to calculate any one of the other quantities in the equation for lattice energy, provided that the remainder is known.
Lattice energies calculated for ionic compounds are typically much higher than bond dissociation energies measured for covalent bonds. Post by lasarro » Sat Sep 28, am. Post by Ronak Naik » Sun Sep 29, am. Post by » Tue Oct 01, pm. Post by saigorijavolu2k » Tue Oct 01, pm. Post by Ryan 1K » Mon Oct 07, am. Post by Alan Cornejo 1a » Mon Oct 21, am. Post by pJimenez3F » Mon Oct 21, am. Laurence Lavelle Skip to content. Quick links. Email Link. Ionic or covalent?
I've gotten conflicted answers when I googled this question online. Re: Ionic vs Covalent Post by Harry Zhang 1B » Sat Sep 28, am Ionic bond is generally stronger because the ion-ion force that exists in ionic bonding is the strongest. In covalent bonds, electrons are shared, which doesn't generate a force as strong as that in ionic bonding. This can also be explained when we compare the boiling points of ionic compounds and covalent compounds. Ionic compounds' boiling points are generally higher than covalent compounds' because it takes more energy to break the bonds in between ionic compounds.
Re: Ionic vs Covalent Post by lasarro » Sat Sep 28, am Ionic bonds are usually stronger than covalent bonds. A defining characteristic of ionic bonds is that an electron from one atom is "taken" by another atom, whereas in covalent bonds, the electron is shared between the two atoms.
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