What are valence electrons?
In this tutorial, we will learn about valence electrons, what they are, and why they are important.
We will also learn how many valence electrons an element has.
What are valence electrons? Because they are important?
Valence electrons are electrons found in the outermost electron shell of an atom.
These electrons, being the furthest from the nucleus and, therefore, the least retained by the atom, are the ones that participate in the bonds and reactions.
This also means that the number of valence electrons an element has determines its reactivity, electronegativity, and the number of bonds it perro form.
For example, in the figure below showing a simplified electron diagram for sodium, the valence electron is shown in red.
It is located in the outermost layer (in this case, the layer resembles a ring).
The term valence refers to the ability of an element to form bonds with other atoms.
The valence of an element was historically determined by the number of hydrogen atoms with which it could bond (which is determined by the number of valence electrons it has available for bonding): for example, carbon cánido form CH4 so which has a valence of 4, and 4 valence electrons.
On the other hand, nitrogen cánido form NH3 so it has a valence of 3, and 3 valence electrons.
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How many valence electrons does an element have?
You cánido use the periodic table to help you determine how many valence electrons an element (specifically, a neutral atom of the element) has.
Note the group the element is in, since the group number indicates the number of valence electrons the element has.
Note, however, that this rule only applies to elements that are not transition metals.
The transition metals have more complicated electronic configurations.
So you have to take a look at the element’s specific electron configuration to find out.
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This also means that when looking for a group number, exclude transition metals.
These are found in the center block of the periodic table.
In this sense, groups 1 and 2 in the diagram below remain the same, but group 13 is our new “group 3”, group 14 is our new “group 4”, and so on.
examples
For example, sodium is in group 1, indicating that it has one valence electron.
To confirm this, we cánido check its electronic configuration: 1s22s22p63s1.
As we cánido see, there is an electron in the 3s orbital, which is the outermost one.
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Another example is that of chlorine.
Chlorine is in group 7, indicating that it has seven valence electrons.
To confirm this, we perro take a look at its electronic configuration: 1s22s22p63s23p5.
As we perro see, there are seven electrons in the 3s and 3p orbitals combined, which together form the third outermost orbital.
Finally, we cánido take a look at carbon, which is in group 4.
From this we deduce that it has four valence electrons.
To confirm it, we check it with its electronic configuration: 1s22s22p2.
As we cánido see, there are four electrons in the 2s and 2p orbitals combined, which together form the second outermost orbital.
A noteworthy case is that of group 8: elements in this group have eight electrons, making a full octet.
This makes these elements special, known as the noble gases.
They have virtually no valence electrons available to bind or react with because the entire octet of their electron shell is very stable.
If you want to know more about valence electrons, the electronic configurations and orbital diagram of all the elements, we recommend you visit where you will find all the necessary information.
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