The quantity of electrons gained or lost by an atom to complete its outermost shell is valency. Atoms are stable when completing their outer shell or an octet (8 electrons in their most outer shell).
They then tend to join with other atoms or participate in chemical reactions. They can shed or give electrons from other molecules or might gain or take electrons taken from other elements to attain a stable state after the completion of their Octet.
The motive behind the bond or chemical reaction that occurs between atoms is that they are constantly in a battle to achieve a stable state after completing their outermost orbit or shell. If, for example, an atom only has one shell and orbit, it is attained when it contains two electrons inside it.
Similarly, if an element has more than two orbits or shells, the stable state is reached in the outermost shell with eight electrons.
For instance, Hydrogen has only one electron within its atom in the largest shell. Therefore, it must somehow add another electron into its outer shell orbit to have complete electrons within its outermost orbit. In the same way, oxygen has an electronic configuration of 2, 6. Thus, it has 6 electrons within its outermost shell or orbit.
Thus, it needs two electrons to complete the orbit.
Here’s the valency Chart
| Element | Symbol | Valency | Atomic Number |
| Hydrogen | H | 1 | 1 |
| Lithium | Li | 1 | 3 |
| Helium | He | 0 | 2 |
| Boron | B | 3 | 5 |
| Beryllium | Be | 2 | 4 |
| Nitrogen | N | 3 | 7 |
| Carbon | C | 4 | 6 |
| Fluorine | F | 1 | 9 |
| Oxygen | O | 2 | 8 |
| Sodium | Na | 1 | 11 |
| Neon | Ne | 0 | 10 |
| Aluminium | Al | 3 | 13 |
| Magnesium | Mg | 2 | 12 |
| Phosphorus | P | 3 | 15 |
| Silicon | Si | 4 | 14 |
| Chlorine | Cl | 1 | 17 |
| Sulphur | S | 2 | 16 |
| Potassium | K | 1 | 19 |
| Argon | Ar | 0 | 18 |
| Calcium | Ca | 2 | 20 |
After going through the valency chart, let’s move further.
How to find the valency of an Element?
Valency is a result of losses or gains of electrons. It is distinct by the number of electrons that make up an atom. For instance, the atomic number for Sodium is 11. Therefore, it contains 11 electrons. However, its valency is one.
Since its electronic distribution is basically (2, 8, 1), it is much easier to lose one electron than gain 7 electrons to stabilise or complete its Octet.
Thus, its valency will be 1.
The valency of oxygen with atomic number 8 and the electronic structure (2, 6) is 2 since adding two electrons to complete its Octet is very easy. However, the atoms of Fluorine with electronic configurations (2, 7) generally gain an electron rather than losing all its seven electrons because it is more convenient for them to gain one electron instead of losing seven electrons.
Therefore its valency is still 1.
Also, there are other elements of the periodic table with a valency of zero, such as noble gases, helium (He), neon (Ne) and Argon (Ar) since they contain eight electrons within their outermost shells, or their octets are complete.
Therefore, they don’t react with other elements, atoms, or elements or are believed to be least reactive, and because of this, they are also referred to for their inert gas properties.
Additionally, the placed charge is an atom after it transforms into an ion after either losing or adding electrons occurs because it has valency.
For example, sodium Ion’s charge will be -1 when it loses an electron during reactions to attain an optimal electronic configuration (2 8.) or achieve an entirely filled outer shell or an orbit. Similar to that, the charge of Magnesium ion after Magnesium loses two electrons + 2 (Mg2+). This is because its electronic arrangement is (2, 8, 2) and, therefore, it is likely to lose two electrons.
What are the valence electrons?
The number of electrons present within the orbit or the energy-shell of an atom is known as the valence electrons. For instance, the electronic configuration of Magnesium is 2, 8, 2. This means that the K orbit has 2 electrons, while the L orbit contains 8 electrons, and the M orbit contains 2 electrons.
Therefore you have two electrons on the outside of Magnesium. Also, it contains 2 electrons in valence. In the same way, Chlorine (Cl), whose electronic configuration is 2, 8, 7, is composed of 7 valence electrons. The outermost layer that has the valence electrons are known as the “valence shell.”
The difference between Oxidation and Valency
The ability to combine an atom is referred to as valency. This is the number of valence electrons an atom can gain or lose in its orbit around the outermost point. The number of oxidations is the charge an atom can carry.
In other words, nitrogen is a molecule with a valency of 3, but its Oxidation number could range between -3 and 5. The oxidation number is an assumption of the charge of the atom of an ion or molecule. It aids in determining the ability that an individual atom has to absorb or release electrons within a specific species.
How do I keep track of Valencies?
If you wish to learn the valencies of elements :
First, learn the names of the elements in the periodic table in order.
When you perform this, you will receive the atomic number—the number of protons. Also, you will be able to determine the number. of electrons. {No. of protons = No. of electrons}
-> Valency is the number of valence electrons that are either gained in an element.
>>> Remember this formula i.e. 2(n)^2. This formula with which we can be aware of the number of electrons contained in an orbit or Shell.
For example, K is the orbit that starts.
Therefore, 2(1)^2 = 2(1) = 2.
K shells can contain two electrons as a maximum limit.
By doing this, we can determine the number of valence electrons, which is the value. Because we know the atomic No. along with the equation, it is possible to calculate the number. of electrons that are present on the outside of the shell/orbit
Conclusion
At some point in our school lives, we’ve faced difficulties while learning the valency table, and also, as there are high chances of the same being asked in the exams, it is vital to learn and remember the table. The core advice is not to waste time applying tips and tricks. Keep it straight, revise it well, and you’ll succeed in memorising valencies!