Chemical Bonds - Gallium Powered

Chemical bonds are a big part of chemistry. The reason why atoms bond is to become more stable by decreasing their energy and filling up their valence shell. It may sound complicated but it's easier than you think. There are different kinds of bonds as different atoms and ions have different preferences.

To understand why atoms bond we have to look at the periodic table. As you see all elements are distributed in groups and periods depending on their atomic number and properties. In the periodic table (only for A groups) the number of the group represents the number of electrons an element has in its valence shell.

For example, Sodium is from IA group which means it has one electron in its valence shell, Oxygen is from VIA group and it has 6 electrons in its valence shell.

All of this sounds good but the problem is that in most cases the valence shell has 8 places (or two if it is the only one shell). And this means that atoms will be stable only if they have 8 electrons in their outer shell. But elements are as they are and only some lucky of them have the chance to be stable by nature and we call them noble gases. Other noble elements like Silver (Ag), and Gold (Au) are stable too but they have only 1 electron in their valence shell but they are from B groups so we will leave them for now.

The first type of bonding we will talk about is the ionic one.

Ionic bonding

This kind of bonding is pretty easy to understand. The only thing you have to know is that opposites attract. In this case, the oppositely charged ions attract to each other.

The ionic bond forms when one or more electrons are exchanged. For example when Sodium (Na) and Chlorine (Cl) bond Sodium gives one electron to the Chlorine and then both of them become ions.

All of this is done because Sodium has only one electron in its valence shell while Chlorine has 7. Both of them don’t have enough to be stable and the only way is to form an ionic bond.

In this case, when Sodium gives one electron it becomes positively charged ion and now its valence shell has 8 electron which is very stable condition but the problem is that this ion cannot exist in nature for too long. On the other side, Chlorine receives one electron which makes it negatively charged ion but it has 8 electrons in its valence shell which makes it stable too.

And when this process ends we have two ions with filled valence shells. Which makes them feel good but then another process takes part. The two ions are oppositely charged so they attract each other. This attraction makes them to bond and this is how ionic bonds are made.

These bonds happen between two or more ions and rely on the fact that opposites attract each other. And on the other side, we got NaCl which is just another word for salt. Sodium and Chlorine really like to be with each other and that's the reason why salt (NaCl) is such a stable compound.

There are a lot of elements which rely on ionic bonds. Now we can see another example this time with Calcium (Ca) and Chloride (Cl). Calcium has 2 electrons in its valence shell which is not as good as it sounds. Chlorine still has 7 electrons as we discussed early so it is still unstable too.

This time Calcium has 2 electrons which it wants to give away but the problem is that Chlorine only needs one. So the solution is more than obvious: Calcium will just have to bond with two Chlorine atoms and we will receive CaCl2.

The process is the same as we told you above. Calcium will get rid of its two electrons and will have 8 in its valence shell which makes it ion with a positive charge (the charge is positive because the element has more protons than electrons) and each of the two Chlorine atoms will receive one electron which makes them ions with a negative charge (negative because the electrons are more than the protons). The oppositely charged ions will attract each other and this will make them bond.

Now we have to discuss covalent bonds which can be polar and non-polar. In the case of ionic bonds, the electrons are exchanged while in covalent bonds electrons are shared. But this sharing is not always equal so we have polar and non-polar covalent bonds.

Covalent bonds

In non-polar covalent bonds, the electrons are shared equally. This means no one of the atoms participating in the bond attracts the electron more than the others. We can see this kind of bonding in some naturally occurring elements like Hydrogen, Nitrogen, Oxygen, Fluorine, Chlorine, Bromine and Iodine. They all form non-polar covalent bonds because as the two participants are still the same element no one can attract the shared electrons more than the other.

In the case of Hydrogen, the element has only one electron because it is number one in the periodic table. As it has one electron it cannot fill its valence shell which is not very good for it but here comes the covalent bonding. When one Hydrogen atom meets another one they can share their electron so they will have two. The two electrons are shared equally and this is a non-polar covalent bonding.

There are several kinds of bonds depending on the number of pairs of electrons shared and how strong they are. There are sigma bonds which are the strongest and pi bonds which are weaker than sigma ones.

When we classify bonds by their pairs of electrons which are shared there are single, double and triple.

In the case of Hydrogen, the bond is a single sigma bond, because there is only one pair of electrons which are shared. And it is non-polar because the electrons are shared equally.

There can be polar covalent bonds too. In the case where different elements bond one of them can desire the electrons more than the other so, it will attract them stronger.

The easiest way to see which element will attract the electrons stronger is to look up to the periodic table. We start from its right top corner where the atoms attract electrons the most and while going diagonally to the left bottom corner of the table we get to the weakest attractors.

On the right top corner of the table, Helium is located but it is noble gas so we exclude all of the noble gases and then what we see is Fluorine. It is the element which desires electrons the most so when it bonds with other elements it will always attract them stronger.

For example, let’s take the compound HF. In this case, the Fluorine has 7 electrons because it is from VIIA group and Hydrogen has 1. None of them is stable and happy so they have to bond in the case to become stable.

When they bond they both share their electrons but Fluorine wants them more so it attracts them stronger. This way the whole compound becomes a little bit polar. When the electrons are concentrated around one of the atoms which participate in the bond this part will become slightly negatively charged while the other will be slightly positively charged. This polarization makes things even more unfair for Hydrogen because electrons will always prefer to stay on the more negative side.

Now when we know more about covalent bonds we can move to Hydrogen bonds. These bonds represent the electrostatic force of attraction between a Hydrogen atom which is in a covalent bond and other elements of the same bond.

Hydrogen bonds

These bonds are very weak so they easily break and that's why they are so important. In the case of water (H20) the whole bond is covalent but between the two Hydrogen atoms and the Oxygen are formed Hydrogen bonds. Their ability to break easily gives the water all of its incredible properties. You don’t think about it every day but this is why water can hold so much heat, can vaporize, ice can float above liquid water and much more.

This is just a small fraction of all the good thinks Hydrogen bonds do. They play a big role in biology.

For example, DNA is held together by these weak bonds. It can sound strange that something so important is not held together by something stronger but it turns out that it is of really big importance for the nitrogen bases which form DNA to be able to form and break bonds when needed. This way the genes can be easily edited and some great and some not so things can happen as a result.

Let’s try to summarize all of the information

Atoms bond to become stable (this is achieved only when the last (valence) shell is filled with electrons (for A groups)). In this lesson, you have learned about 3 types of bonds: ionic, covalent and hydrogen. These bonds are all different because in different compounds the different elements need different things.

Ionic bonds are based on the electrostatic attraction of the positively charged ions which form when electrons are exchanged.

Covalent bonds are bonds formed between nonmetals and in their cases, electrons are shared instead of given and taken. When the electrons are equally shared the bonds are nonpolar but the sharing is not always equal so there are polar covalent bonds too.

And finally, hydrogen bonds which are formed between hydrogen atoms which are extremely important for a lot of things like the incredible qualities of water, the structure of our DNA and so on.