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What is the strongest bond in chemistry in order?

What is the strongest bond in chemistry in order?

Another way the octet rule can be satisfied is by the sharing of electrons between atoms to form covalent bonds. These bonds are stronger and much more common than ionic bonds in the molecules of living organisms. Covalent bonds are commonly found in carbon-based organic molecules, such as our DNA and proteins. Covalent bonds are also found in inorganic molecules like H2O, CO2, and O2. One, two, or three pairs of electrons may be shared, making single, double, and triple bonds, respectively. The more covalent bonds between two atoms, the stronger their connection. Thus, triple bonds are the strongest.

The strength of different levels of covalent bonding is one of the main reasons living organisms have a difficult time in acquiring nitrogen for use in constructing their molecules, even though molecular nitrogen, N2, is the most abundant gas in the atmosphere. Molecular nitrogen consists of two nitrogen atoms triple bonded to each other and, as with all molecules, the sharing of these three pairs of electrons between the two nitrogen atoms allows for the filling of their outer electron shells, making the molecule more stable than the individual nitrogen atoms. This strong triple bond makes it difficult for living systems to break apart this nitrogen in order to use it as constituents of proteins and DNA.

The formation of water molecules provides an example of covalent bonding. The hydrogen and oxygen atoms that combine to form water molecules are bound together by covalent bonds. The electron from the hydrogen splits its time between the incomplete outer shell of the hydrogen atoms and the incomplete outer shell of the oxygen atoms. To completely fill the outer shell of oxygen, which has six electrons in its outer shell but which would be more stable with eight, two electrons (one from each hydrogen atom) are needed: hence the well-known formula H2O. The electrons are shared between the two elements to fill the outer shell of each, making both elements more stable.

View this short video to see an animation of ionic and covalent bonding.

Polar and Nonpolar Covalent Bonds

There are two types of covalent bonds: polar and nonpolar. Nonpolar covalent bonds form between two atoms of the same element or between different elements that share the electrons equally. For example, an oxygen atom can bond with another oxygen atom to fill their outer shells. This association is nonpolar because the electrons will be equally distributed between each oxygen atom. Two covalent bonds form between the two oxygen atoms because oxygen requires two shared electrons to fill its outermost shell. Nitrogen atoms will form three covalent bonds (also called triple covalent) between two atoms of nitrogen because each nitrogen atom needs three electrons to fill its outermost shell. Another example of a nonpolar covalent bond is found in the methane (CH4) molecule. The carbon atom has four electrons in its outermost shell and needs four more to fill it. It gets these four from four hydrogen atoms, each atom providing one. These elements all share the electrons equally, creating four nonpolar covalent bonds.

In a polar covalent bond, the electrons shared by the atoms spend more time closer to one nucleus than to the other nucleus. Because of the unequal distribution of electrons between the different nuclei, a slightly positive (δ+) or slightly negative (δ–) charge develops. The covalent bonds between hydrogen and oxygen atoms in water are polar covalent bonds. The shared electrons spend more time near the oxygen nucleus, giving it a small negative charge, than they spend near the hydrogen nuclei, giving these molecules a small positive charge. Polar covalent bonds form more often when atoms that differ greatly in size share electrons.

Examples of Covalent Bonding

Table compares water, methane and carbon dioxide molecules. In water, oxygen has a stronger pull on electrons than hydrogen resulting in a polar covalent O-H bond. Likewise in carbon dioxide the oxygen has a stronger pull on electrons than carbon and the bond is polar covalent. However, water has a bent shape because two lone pairs of electrons push the hydrogen atoms together so the molecule is polar. By contrast carbon dioxide has two double bonds that repel each other, resulting in a linear shape. The polar bonds in carbon dioxide cancel each other out, resulting in a nonpolar molecule. In methane, the bond between carbon and hydrogen is nonpolar and the molecule is a symmetrical tetrahedron with hydrogens spaced as far apart as possible on the three-dimensional sphere. Since methane is symmetrical with nonpolar bonds, it is a nonpolar molecule.

Figure 1. Whether a molecule is polar or nonpolar depends both on bond type and molecular shape. Both water and carbon dioxide have polar covalent bonds, but carbon dioxide is linear, so the partial charges on the molecule cancel each other out.

Video Review

Watch this video for another explanation of covalent bonds and how they form:

Chemical Bonding

Chemical compounds are formed by the joining of two or more atoms. A stable compound occurs when the total energy of the combination has lower energy than the separated atoms. The bound state implies a net attractive force between the atoms . a chemical bond. The two extreme cases of chemical bonds are:

Covalent bond: bond in which one or more pairs of electrons are shared by two atoms.

Ionic bond: bond in which one or more electrons from one atom are removed and attached to another atom, resulting in positive and negative ions which attract each other.

Other types of bonds include metallic bonds and hydrogen bonding. The attractive forces between molecules in a liquid can be characterized as van der Waals bonds.

Covalent Bonds

Covalent chemical bonds involve the sharing of a pair of valence electrons by two atoms, in contrast to the transfer of electrons in ionic bonds. Such bonds lead to stable molecules if they share electrons in such a way as to create a noble gas configuration for each atom.

Hydrogen gas forms the simplest covalent bond in the diatomic hydrogen molecule. The halogens such as chlorine also exist as diatomic gases by forming covalent bonds. The nitrogen and oxygen which makes up the bulk of the atmosphere also exhibits covalent bonding in forming diatomic molecules.

Covalent bonding can be visualized with the aid of Lewis diagrams.
Comparison of ionic and covalent materials.


Polar Covalent Bonds

Covalent bonds in which the sharing of the electron pair is unequal, with the electrons spending more time around the more nonmetallic atom, are called polar covalent bonds. In such a bond there is a charge separation with one atom being slightly more positive and the other more negative, i.e., the bond will produce a dipole moment. The ability of an atom to attract electrons in the presense of another atom is a measurable property called electronegativity.

Ionic Bonds

In chemical bonds, atoms can either transfer or share their valence electrons. In the extreme case where one or more atoms lose electrons and other atoms gain them in order to produce a noble gas electron configuration, the bond is called an ionic bond.

Typical of ionic bonds are those in the alkali halides such as sodium chloride, NaCl.

Ionic bonding can be visualized with the aid of Lewis diagrams.
Comparison of ionic and covalent materials.
Energy contributions to ionic bonds
Table of ionic diatomic bonds


Metallic Bonds

The properties of metals suggest that their atoms possess strong bonds, yet the ease of conduction of heat and electricity suggest that electrons can move freely in all directions in a metal. The general observations give rise to a picture of «positive ions in a sea of electrons» to describe metallic bonding. Such bonds are neither ionic nor covalent since the participating electrons are not localized on the atoms.

Metal Properties

The general properties of metals include malleability and ductility and most are strong and durable. They are good conductors of heat and electricity. Their strength indicates that the atoms are difficult to separate, but malleability and ductility suggest that the atoms are relatively easy to move in various directions. The electrical conductivity suggests that it is easy to move electrons in any direction in these materials. The thermal conductivity also involves the motion of electrons. All of these properties suggest the nature of the metallic bonds between atoms.

Hydrogen Bonding

Hydrogen bonding differs from other uses of the word «bond» since it is a force of attraction between a hydrogen atom in one molecule and a small atom of high electronegativity in another molecule. That is, it is an intermolecular force, not an intramolecular force as in the common use of the word bond. As such, it is classified as a form of van der Waals bonding, distinct from ionic or covalent bonding.

When hydrogen atoms are joined in a polar covalent bond with a small atom of high electronegativity such as O, F or N, the partial positive charge on the hydrogen is highly concentrated because of its small size. If the hydrogen is close to another oxygen, fluorine or nitrogen in another molecule, then there is a force of attraction termed a dipole-dipole interaction. This attraction or «hydrogen bond» can have about 5% to 10% of the strength of a covalent bond.

Hydrogen bonding has a very important effect on the properties of water and ice. Hydrogen bonding is also very important in proteins and nucleic acids and therefore in life processes. The «unzipping» of DNA is a breaking of hydrogen bonds which help hold the two strands of the double helix together.

What is the strongest bond in chemistry in order?

Chemical Bonds

When atoms of different elements combine together they form compounds. Familiar compounds include common table salt (Sodium Chloride) and water. Table salt is made from a combination of atoms of sodium (Na) and chlorine (Cl) in a ratio of 1:1 forming the compound NaCl. Water is a combination of hydrogen (H) and oxygen (O) is a ration of 2:1 forming the compound H2O.

There are different types of chemical bonds. Some bonds involve a transfer of electrons. Others involve a sharing of electrons. Still other bonds are weak attractions between molecules. Let’s look at each type of bond.

Ions are formed by atoms that have non-full outermost electron shells in order to become more like the noble gases in Group 8 of the Periodic Table (see section on ions). Some atoms add electrons to get a full shell, thus becoming a negative ion. Other atoms subtract electrons from their outermost shell, leaving a full shell and an overall positive charge on the ion. In the previous section, we saw that atoms with fewer than 4 electrons in their outermost shell tend to form positive ions, and those with more than 4 electrons tend to form negative ions. Ionic bonds form when atoms transfer electrons between each other, forming ions that are electrically attracted to each other forming a bond between them. Sodium chloride (NaCl) is a typical ionic compound. The picture below shows both a sodium and a chlorine ion.

Sodium has 1 electron in its outermost shell, and chlorine has 7 electrons. It is easiest for sodium to lose its electron and form a +1 ion, and for chlorine to gain an electron, forming a -1 ion. If sodium can transfer it’s «spare» electron to chlorine (as shown above), both atoms will satisfy their full outer shell requirements, and an ionic bond will be formed. If large groups of sodium and chlorine atoms bond this way, the result is a three-dimensional structure with alternating sodium and chlorine ions:

The blue dots are the sodium atoms; the pale green dots are the larger chlorine atoms. Ionic bonds between each atom forms a relatively strong bond and a three-dimensional, cubic structure. Below is a look at just a single layer:

Note that each positive sodium ion is next to a negative chlorine ion. Now imagine this arrangement continuing outward in all directions with thousands of billions of atoms. Wow!

2. Covalent Bonds.

Sometimes atoms will share electrons instead of transferring them between the two atoms. This sharing allows both atoms to fill their outermost shell while forming a very strong bond between the atoms. Elements such as carbon (C) and Silicon (Si) form strong covalent bonds. Below is a picture showing the electron sharing that occurs in the mineral diamond. Diamonds are made of pure carbon and its the way that the carbon atoms are bonded that makes diamond the hardest substance.

Each carbon atom has 4 electrons (blue dots) in its outer shell. This allows the atom to share electrons with 4 other carbon atoms surrounding it (as the middle carbon atom is doing). Each of these in turn will share the remaining 3 electrons with adjacent carbon atoms beside, above and below it, and those with other carbon atoms, etc., forming a interlocking, three-dimensional network of tightly bonded carbon atoms. Similarly, covalent bonding between silicon and oxygen atoms makes strong bonds that form a large group of minerals called silicates (more on those later).

3. Metallic and Van der Waals Bonds.

Metallic bonds form when the outer shell electrons are shared between neighboring atoms. Unlike covalent bonding however, there are insufficient numbers of electrons in most metal atoms (such as copper or silver) to form pure covalent bonds. Therefore, the electrons are shared amongst all the nearest neighbor metal ions, forming a metallic bond. This strange arrangement of «metallic ions is a sea of electrons» gives metals their particular physical properties.

Metallic bonds are also explained by band theory. Band theory states that closely packed atoms have overlapping electron energy levels resulting in a conduction «band» wherein the electrons are free to roam between atoms, thus bonding them together. For more information on metallic bonds and band theory, see this web site.

Van der Waals bonds are weak bonds that form due to the attraction of the positive nuclei and negative electron clouds of closely packed atoms. This attraction is opposed by the repulsive force of the electron clouds and the repulsive force of neighboring nuclei. However, the attraction is stronger than the total repulsive forces, leaving a residual, weak attraction. Van der Waals bonding is important in minerals such as graphite and clay minerals.

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