Why are covalent bonds weaker than ionic bonds?

Answer 1

The short answer is that they are not always weaker in fact. Some ionic compounds have very strong bonds, while some covalent bonds are quite weak. Usually however, it is easier to break an ionic bond than a covalent one. What determines the actual strength of a bond is quite complex, but let me try to explain the basic principles. Bonding has everything to do with electrons. In ionic bonds, an element loses an electron to another element. The two elements are then bonded by a force of attraction based on electrostatics, or Coulombic force; it is due to the fact that a positive charge and a negative charge attract each other (like the two opposite ends of a magnet). Since one element has a negative charge and the other has a positive charge they are held together in a bond. I will give an example. Sodium chloride, NaCl, or more commonly known as table salt, is an ionically bonded compound. The sodium, Na, will lose one electron (to form a Na+ ion), and the chlorine, Cl, will gain that electron (to form a Cl- ion). Since an electron has a negative charge, the sodium has a positive charge (lost a negative), and the chlorine has a negative charge (gained a negative). Just like north and south magnets, the two are attracted to each other and are bonded. The bond strength is determined by how much charge each element has. For instance, you can also have ions that have more than one charge. Common ions like this are Mg2+, Fe3+, and O2-. Because each ion has more than one charge, the attraction is even stronger because the Coulombic force is directly related to the size of the charge on each ion. In covalent bonds, elements share electrons. No electrons are given away or taken completely, but are instead shared between the elements. For example, Nitrogen gas, or N2 is simply two nitrogen atoms bonded together. There is no reason for one N to give an electron to the other one. They both want to hold on to their electrons exactly the same amount! (As opposed to NaCl in the example above, where Cl needs an extra electron, and Na needs to get rid of one to become most stable). The strength of a covalent bond is determined by a complicated set of properties of the atoms involved. What makes a covalent bond weak or strong is really beyond the scope of this discussion. (Briefly, the strength of covalent bonds is related to the nature of the atomic orbitals involved in the bond, specifically the overlay of the orbitals involved in the bond, and the size of the energy difference between the orbitals. If that doesn't make sense, don't worry too much about it... it's complicated stuff!) In general, ionic bonds are easier to break, but it depends on several factors. For instance, breaking ionic bonds is very easy to do when you dissolve an ionic compound in water. Water is special because it effectively reduces this Coulombic attraction between the plus and minus charges on the ions (it kind of acts like a barrier or shield, blocking the plus from seeing the minus). However, if you were trying to break an ionic bond in a perfect vacuum, it would be much harder (because without something to block the attractive force, it is quite strong). Another thing to consider is that ionic compounds usually form 3-dimensional crystals, where there are many many ionic bonds, whereas covalent bonds tend to be found in isolated molecules (except for network covalent compounds like diamond or silicon). The fact that ionic bonds form a 3-D structure in a crystal makes a huge difference. So part of what makes this question so complicated is that you kind of comparing apples and Oranges.

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Answer 2

The short answer is that they are not always weaker in fact. Some ionic compounds have very strong bonds, while some covalent bonds are quite weak. Usually however, it is easier to break an ionic bond than a covalent one. What determines the actual strength of a bond is quite complex, but let me try to explain the basic principles. Bonding has everything to do with electrons. In ionic bonds, an element loses an electron to another element. The two elements are then bonded by a force of attraction based on electrostatics, or Coulombic force; it is due to the fact that a positive charge and a negative charge attract each other (like the two opposite ends of a magnet). Since one element has a negative charge and the other has a positive charge they are held together in a bond. I will give an example. Sodium chloride, NaCl, or more commonly known as table salt, is an ionically bonded compound. The sodium, Na, will lose one electron (to form a Na+ ion), and the chlorine, Cl, will gain that electron (to form a Cl- ion). Since an electron has a negative charge, the sodium has a positive charge (lost a negative), and the chlorine has a negative charge (gained a negative). Just like north and south magnets, the two are attracted to each other and are bonded. The bond strength is determined by how much charge each element has. For instance, you can also have ions that have more than one charge. Common ions like this are Mg2+, Fe3+, and O2-. Because each ion has more than one charge, the attraction is even stronger because the Coulombic force is directly related to the size of the charge on each ion. In covalent bonds, elements share electrons. No electrons are given away or taken completely, but are instead shared between the elements. For example, Nitrogen gas, or N2 is simply two nitrogen atoms bonded together. There is no reason for one N to give an electron to the other one. They both want to hold on to their electrons exactly the same amount! (As opposed to NaCl in the example above, where Cl needs an extra electron, and Na needs to get rid of one to become most stable). The strength of a covalent bond is determined by a complicated set of properties of the atoms involved. What makes a covalent bond weak or strong is really beyond the scope of this discussion. (Briefly, the strength of covalent bonds is related to the nature of the atomic orbitals involved in the bond, specifically the overlay of the orbitals involved in the bond, and the size of the energy difference between the orbitals. If that doesn't make sense, don't worry too much about it... it's complicated stuff!) In general, ionic bonds are easier to break, but it depends on several factors. For instance, breaking ionic bonds is very easy to do when you dissolve an ionic compound in water. Water is special because it effectively reduces this Coulombic attraction between the plus and minus charges on the ions (it kind of acts like a barrier or shield, blocking the plus from seeing the minus). However, if you were trying to break an ionic bond in a perfect vacuum, it would be much harder (because without something to block the attractive force, it is quite strong). Another thing to consider is that ionic compounds usually form 3-dimensional crystals, where there are many many ionic bonds, whereas covalent bonds tend to be found in isolated molecules (except for network covalent compounds like diamond or silicon). The fact that ionic bonds form a 3-D structure in a crystal makes a huge difference. So part of what makes this question so complicated is that you kind of comparing apples and Oranges.

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Answer 3

What sort of bonding are you saying that is weaker than covalent bonding? I think you need to reword your question. If this is relevant... Covalent bonding is the strongest sort of bonding (which makes it under the category of bonding so your question is chemistry and grammatically incorrect). It is like this because all valence shells are full and don't want to gain or lose any electrons. This makes them extremely unreactive and requires great heat to undo them and even with that, it takes ages. I think you need to research about this topic a little more if you don't understand what I'm talking about. Ionic Bonding is stronger than covalent bonding actually.

Answer 4

So to answer your question, substances with standard ionic bonds seem to be weaker than those with covalent bonds because the covalent bonds tend to form a lattice structure, that makes them much stronger.

Answer 5

Covalent bonds share electrons where as ionic bonds "trade" electrons. The atoms in a covalent bond are only getting half of what they want and are "tricked" into thinking they have a full valence shell.

Answer 6

Molecules are electrically neutral; they contain equal numbers of positively charged protons and negatively charged electrons (often in a complicated arrangement). Portions of a molecule may have some degree of electrical charge because the charges within a molecule are unevenly distributed. For example, a water molecule is slightly negative where the oxygen atom is and slightly positive where the hydrogen atoms are. Ions, in comparison, have electrical charges, because they have either lost or gained electrons. Since all these forces, both the ionic bonds and the intermolecular forces, derive from electrostatic forces as described by Coulomb's Law, the greater the difference in charge, the greater the resulting force. Charged ions must necessarily exert more force than uncharged molecules.

Answer 7

There are two different questions here:

1) What are covalent bonds? -- Covalent bonds, most simply, occur when two atoms "decide" to share elections in order to complete their outermost electron shell. In a covalent bond, each atom will donate the same number of electrons to be shared (between 1-3 for single, double, or triple bonds) to a communal pool of electrons that overlaps both atoms' electron shells.

2) Why do chemists say that covalent bonds are weaker than ionic bonds? -- Chemists say it because it is actually true. An ionic bond is created through the transfer of one or more electrons from one atom to another. This results in the donating atom becoming positively charged and the receiving atom becoming negatively charged. This creates an electromagnetic force that acts upon the atoms, which is quite strong. Conversely, with a covalent bond the two positively charge nuclei are very close, creating an electromagnetic force that threatens to break the bond. As a result, the bond has to overcome the electromagnetic force instead of becoming strengthened by it.

There are a number of properties that ionic compounds have that further show the strength of their bonds. Ionic compounds melt and boil at much higher temperatures than covalently bonded substances (as a general rule). Ionic compounds form tessellations rather than individual molecules and bond strength does not attenuate with repetitive bonding.

Answer 8

This relates to structure and bonding. In ionic compounds, there are very strong electrostatic attraction between the oppositely charged ions in a crystal lattice of giant ionic structure. In covalent compounds, there are comparatively weak covalent bonds between the molecules, so less energy will be required to overcome these bonds.

Answer 9

Ionic compounds are held together by strong electostatic forces whereas covalent compounds are held together by weak Vaan der Waal forces. Because of this covalent compounds have lower Inter molecular forces and there by are weaker in comparison to ionic compounds.

Answer 10

becasue of the attractions in the ples amd atoms