Bonding is one of the most fundamental aspects of chemistry. All matter is made up of atoms that are bonded together, and the type of bond that is formed between atoms determines much of its properties.
There are three major types of bonds: covalent, ionic, and polar covalent. Each bond type is characterized by its structure and the electrostatic force that holds the atoms together.
Covalent bonds are perhaps the easiest to understand. In a covalent bond, two atoms share one or more pairs of electrons. Because the electrons are being shared, this makes it a non-electrostatic bond.
Ionic bonds are characterized by two different atoms that have an unequal charge relative to each other. One atom has a positive charge while the other has a negative charge, and they bind because of this charge difference.
Polar covalent bonds are similar to ionic bonds in that there is an electrostatic component to the bond. The difference is that in a polar covalental bond, one atom has a positive charge while the other has a negative charge.
Oxygen and hydrogen
Another pair of elements that commonly form molecules is oxygen and hydrogen. When atoms of these two elements combine, the bond between them can be covalent, polar covalent, or ionic.
When oxygen and hydrogen atoms combine, the resulting molecule is water. Because water is such a common substance, you might think you could easily determine whether the bonds within it are covalent, polar covalent, or ionic. But it can be more complicated than you think!
That’s because there are different types of bonds within water molecules. A water molecule consists of one oxygen atom and two hydrogen atoms linked together by a covalent bond. This makes up about 50% of the total bond in a water molecule. The other 50% of the bonds are ionic bonds between the oxygen and hydrogen atoms.
Nitrogen and hydrogen
A bond between nitrogen and hydrogen is one of the most common molecules in the world: ammonia. Ammonia is a liquid that can evaporate very easily, which makes it useful for cleaning and other applications.
Ammonia is a compound composed of nitrogen and hydrogen, with three hydrogen atoms per molecule. The way you determine if the bond between each pair of atoms would be pure covalent, polar covalent, or ionic depends on how many hydrogens there are.
If there are no hydrogens, then the bond would be purely covalent. If there are one or more hydrogens, then the bond would be ionic. The middle ground, where there are two hydrogen atoms per nitrogen atom, is where it gets tricky. It could be either type of chemical bonding depending on the situation.
Nitrogen and oxygen
A bond between nitrogen and oxygen is one of the most important pairs in ionic compounds. Many minerals, such as calcium carbonate, rely on this pair for their structure.
When designing a molecule, you must determine if the bond between these atoms would be pure covalent, polar covalent, or ionic.
If the atom pair shares electrons equally, it is considered a pure covalent bond. If one atom shares its electrons with the other atom, it is considered a polar covalent bond. If one atom takes the electrons of the other atom, it is considered an ionic bond.
These distinctions are important because they tell you what kind of molecules you are dealing with and how to break them down. For example, knowing that calcium carbonate contains only ionic bonds between atoms allows you to know how to break it down.
Carbon and hydrogen
When you have carbon atoms with hydrogen atoms attached, it can be difficult to determine the type of bond between them. This is because hydrogen is a very lightweight atom, and carbon is a very strong atom.
When you have a large difference in the atomic mass of two atoms together, it indicates that there is a difference in strength of the bond. A stronger bond will be one that requires more energy to break.
How can we tell if the bond between these two atoms is covalent or not? Well, if the bond between these atoms is covalent then it would be impossible to separate them without breaking the bonds between the carbon and hydrogen atoms.
Therefore, if we test whether or not this compound is volatile or not by burning it, then we know that it is not covalent but either polar covalent or ionic.
Carbon and oxygen
A bond between carbon and oxygen is called carbon dioxide. This molecule consists of one carbon atom and two oxygen atoms. Carbon dioxide is a gas at room temperature and pressure.
Carbon dioxide is produced during the combustion of fossil fuels like oil, natural gas, and coal. It is also produced by plants during photosynthesis when the plants use glucose as a source of energy.
When plants or substances containing carbon are burned, the oxygen in the atmosphere combines with them, leaving behind only carbon dioxide. This process is called oxidation.
Carbon dioxide can be liquefied and refrigerated, turning it into what we call dry ice. When it melts or boils, it returns to a gas.
Hydrogen and nitrogen
Two very common elements that can cause confusion in bond types are hydrogen and nitrogen. These two atoms can create very unique bonds when attached to other atoms.
Hydrogen is an extremely common element, making up a large percentage of our universe. It is most commonly seen as H2, water, but it can also be found in substances such as methane.
When hydrogen is bonded to a heavier atom like nitrogen, it becomes more difficult to pull the atoms apart than with another hydrogen atom. This is because the covalent bond between the two is stronger.
The problem comes when you have a hydrogen atom bonded to a heavier atom like nitrogen. In this case, the bond between them is an ionic bond, not a covalent one. The reason for this is that one of the atoms has an electric charge, making the bond impossible to break without adding energy.
Helium and neon
When two atoms bond by sharing their valence electrons, the bond is called covalent. When atoms bond by sharing both their valence electrons and their nucleus, the bond is called polar covalent. When atoms bond by sharing only their nucleus, the bond is called ionic.
When determining if a covalent bond is pure or polar, the answer lies in the angular distribution of the electron pair. If the pair of electrons orbit in opposite directions, then it is a polar covalent bond. If one electron in the pair orbits in the opposite direction as the other, then it is a pure covalent bond.
Ionic bonds are always characterized by having a full outer shell of electrons for one or both of the atoms involved in bonding. This means that one atom loses or gains enough electrons to fill its outer shell, which then becomes neutral. The other atom takes these lost electrons and uses them to form its own outer shell, making it neutral as well.
Fluorine and chlorine
The bond between each pairs of atoms in molecules containing fluorine and chlorine is always ionic. This is because fluorine can only attach to certain atoms, and chlorine can only attach to certain atoms.
When fluorine attaches to a molecule, it can only attach to hydrogen. When chlorine attaches to a molecule, it can only attach to oxygen. These two elements cannot be paired with each other, so the bond must be ionic.
Ionic bonds are always extremely strong due to the number of electrons that are being transferred between the molecules. This makes them hard to separate and dissolve in water!
Beware when working with these chemicals as they will likely remain solid and stick together even after being poured into water.
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