Valence Electrons Definition – To Help You Understand Chemistry Better


Reading time

6 minutes

Valence Electrons Definition – To Help You Understand Chemistry Better

Valence Electrons Definition – They are described best as those electrons which take part in chemical reactions because they take part in chemical bond formation with other atoms. Valence electrons are usually located in the outermost shell of an atom, which is called the valence shell. However, in the case of transition metals they can be located in an inner shell. These valence electrons determine how an element behaves when it comes into contact with other elements.

The Structure of an Atom

Each atom in an element is made up of a proton, neutron and electrons. Together, the proton and neutron form the positive nucleus, while the negative electrons circle the atom in shells. Each element has a different number of shells depending on how many electrons it has in its ground state. These electrons fill up the shells from the inside out.

Chemical Reactions and Bond Formation

It is due to valence electrons that violent chemical reactions sometimes take place between different elements when they come into contact with each other. This is one of the exciting parts of chemistry, but it is important to understand what is happening at an atomic level rather than just enjoying the spectacle when two elements react. Truly understanding its definition can help clear this up, but let’s look in more detail at how they work.

It is a chemical bond formation that causes the reactions we spoke about. Some elements are very stable while others are volatile, and this is determined by the amount of valence electrons in the outer shell of the atom. When two atoms collide it is the valence shell of each which comes into contact with the other. These electrons are located furthest from the nucleus of the atom and so are not held as tightly as those on the inner shells. In fact, as every atom wants to achieve a stable number of electrons it essentially latches on to the other atom in order to give, take or share electrons. Hint: Try memorising valence definition, it is a building block in chemistry.

Ionic bonds are formed when one atom takes an electron from the other atom. Covalent bonds come about when each of the two atoms in the reaction provide one valence electron which then forms a pair. This process makes each atom more stable than it was before. Tip: Valence definition has three parts to it, this can help you learn it faster

Grouping within the Period Table

The Valence Electrons Definition is reflected on the Periodic Table of Elements. The elements which have the same amount of valence electrons in their outer shells are all put together in groups. This makes it easy to understand which elements behave in a similar way. Within a group, all the elements possess the exact same amount of valence electrons. However, the number of shells increase by one as you go down. Remember, Valence electron definition’s first part – they are electrons which partake in bond formation.

In the metal groups, elements which are at the top of the group are more stable, and therefore less reactive than those further down the group. While the non-metal groups get more reactive as you go up the group, and the less reactive ones are at the bottom. Remember: Valence electron definition’s second part – they are on the outer shell most of the time

Transition Metals

The transition metals are a group of metals which occupies the centre of the Periodic Table of Elements. They are the elements of groups 3 to 12 and they have a high melting and boiling point. The valence electrons of these elements are adhered to the atoms in quite a loose manner. In these metals, the elements are made stable when electrons are shared out among lots of atoms. This creates a lattice style configuration of positive ions which are secured with electrons from other shells. Remember, Valence electron definition’s third part – they control how an element behaves.

Noble Gases

We spoke about elements being what we call ‘stable’, this comes about when the valence shell is full. The Octet Rule tells us that the outer shell can hold 8 electrons at a maximum as this is the most secure composition. However, most elements don’t have this arrangement. The only ones that do are the ones called the noble gases. Because they have a full 8 electrons in their outer shell, they do not need to react with any other elements and so are what we call ‘inert’. This is another word for dormant or lifeless. The noble gases are found on the far side of the Periodic Table of Elements in group 18. They include Helium and Argon. Can you remember what the Valence Electrons Definition is yet?

The other elements across the Periodic Table of Elements are eager to fill up their outer shells as best as they can and so interact with other elements when they get the chance to form bonds. In doing so they can either gain, lose or share electrons depending on their individual needs.

Metals only hold onto their valence electrons quite loosely so they are most likely to lose them to gain the correct configuration. When it achieves this state, it acts more like a noble gas, as described above. Non-metals, however, hold onto theirs with some force and so are more likely to gain electrons from other elements. When an atom gives away electrons, it then has more protons in its nucleus and so becomes a positive ion.


The number of valence electrons also dictates the electro-conductivity of an element. This is the degree to which an element acts most like a metal or an insulator. If an element has high electro conductivity, it is a metal, if it has a low one it is an insulator and if it lies in the middle it is what is known as a semiconductor. Metals have fewer valence electrons and therefore wants to give them away, this valence electron can move away when an electric current is applied and therefore means that metals have high conductivity. Non-metals have more valence electrons and want to hold onto them – and get more, to fill up their shells so they have low conductivity. Need to remind yourself definition? That’s ok, it can be hard to get these chemistry principles straight, but they really do help open up a whole world of scientific possibilities.

Valency versus Valence Electrons

It is important not to get confused between the two similar terms, valence electrons and valency. Although these words sound quite similar, their meaning is not the same and they are certainly not interchangeable. Let’s see why.

As explained above, the valence electrons definition is that they are the electrons which partake in chemical reactions and make bonds with other atoms. They number an element possesses contributes to how it behaves in terms of reactivity and conductivity.

On the other hand, valency is the word which describes just how many bonds and element is able to form. Valency correlates to quantity. It tells us how many bonds can be created between atoms while valence electrons themselves are the particular electrons which actually make up the bonds. IUPAC, the International Union of Pure and Applied Chemistry, supply definitions for many aspects of chemistry. In this case, the definition for valency is ‘the maximum number of univalent atoms (originally hydrogen or chlorine atoms) that may combine with an atom of the element under consideration, or with a fragment, or for which an atom of this element can be substituted’. To reiterate, valency is not the same as valence electrons definition.

We have provided a valence electrons definition and explained what they do and how they contribute to an element’s features. We then explored what the difference between them and valency is to help ensure that you don’t get the two confused.

With the help of this information you will really understand just what is happening the next time you see a chemical reaction occurring, be it in the science lab or out in the real world.

Originally published Jun 27, 2017, updated Feb 19, 2021

Confusing homework?

Get expert help in any course or subject

Get Help