Science of Chemical Bonding
You know that atoms are the basic building blocks of all types of matter. Everything around you—the food you eat, the water you drink, your pets, your toys and even your bodies—is made up of atoms. In nature, these atoms combine with other atoms through chemical bonds which are a result of the strong attractive forces that exist between the atoms.
These atoms are so very tiny that you can only see them under a microscope. Now how can a tiny thing like an atom be useful to us? Well, just like the Lego blocks, these miniscule atoms make themselves useful by combining themselves with each other.
What is chemical bonding?
When two atoms combine with each other, the chemical process that takes place is known as chemical bonding. The electrons that help in the formation of chemical bonds are known as valence electrons, the ones that are found in an atom’s outermost shell. When two atoms come close to each other, the valence electrons in their outer shell interact with each other. Though electrons repel each other, they are attracted to the protons in the nuclei of atoms. Due to the interaction of forces, some atoms form bonds with each other and stick together.
Types of chemical bonding
There are two main types of bonds formed between atoms: ionic bonds (also known as electrovalent bonds) and covalent bonds. An ionic bond is formed when one atom either accepts or donates one or more of its valence electrons to another atom. A covalent bond is formed when instead of donating or accepting electrons, the atoms share valence electrons. When the atoms do not share the electrons equally, a polar covalent bond is formed. When metallic atoms share their electrons, a metallic bond is formed.
Why do atoms form bonds?
Now that you have understood how the atoms combine together, you must also know why these atoms need to bind together. The answer is : all atoms want to be happy, just like you! And what makes them happy is having their shells full. There is a specific 2-8-8 rule that can make them happy. The first shell should be filled with 2 electrons, the second with 8 electrons, and the third one also with 8 electrons.
Some atoms have extra electrons in their shells. These atoms are very generous and always ready to give up their electrons. Some atoms have a few electrons less in their shells. These are the greedy ones, always looking to bag some electrons from other atoms.
Examples of chemical bonds
Let us study some elements, sodium and fluorine for starters, to comprehend the concept of chemical bonding better. Sodium (Na) has 3 shells and only one electron in its outer shell. Now this sodium atom can do either of the two things: it can donate one electron in its third shell to some other atom and have two complete shells, with 8 electrons in each orbit or it can can keep looking for some benevolent atom with extra electrons to meet it someday sometime and fill up its third shell. Which option sounds easier to you? Obviously, it is the first one! It is much easier for the atoms to give away the electrons rather than keep waiting to receive some extra ones.
The atom of another element, fluorine (F) has 7 electrons in its outer shell, i.e. it is one electron shy of becoming ‘happy’. So, what these two atoms do is that they give and take electrons from their outer shells and become happy. In other words, the sodium atom gives away the extra electron in its outer shell to the fluorine atom and then both have a total of 8 electrons in their outermost shell. Such a bond is known as ionic bond. When an atom gives up an electron, it develops a positive charge like sodium (Na+) and when an atom receives an extra electron, it becomes negatively charged like fluorine (F-). The positive and negative charges attract each other like magnets and this is what helps in the formation and maintenance of the bond.
Bonding of Oxygen and Fluorine
Now let us learn more about the covalent bonds with the help of oxygen (O) and fluorine (F). Oxygen has 6 electrons in its outer shell and fluorine has 7. Fluorine needs one electron and oxygen needs a couple of electrons to have a completely filled up shell. Both these elements have innermost shells that are complete with two electrons, but their second shells want to have more! If they agree to share their electrons with atoms of other elements, they can share electrons and make covalent bonds with those elements. They can also decide to make an ionic bond if they prefer to borrow electrons from some other atom rather than sharing. Whether by sharing, donating or borrowing electrons, the atoms of an element reach the happy state of having eight electrons in their outer shells by bonding with other atoms. After all, everyone wants to be happy, right?