Chlorine valence electrons and its use: 7 or 8? Here’s What You Should Know

You might often encounter terms related to the usage of chlorine in chemistry, but wondering about its valence electrons might raise some questions. Consider the following scenarios:

Does chlorine have 7 or 8 valence electrons? 

Can Cl have 14 valence electrons? 

Why isn’t its valency 1 instead of 7?

Regardless of your stance, I think working through the problems sequentially helps solve the paradox.

What Is the Valence Electron of Cl?

Let’s go through the basics first.

Chlorine lies within the halogens group and has an atomic number of 17. The configuration within its electrons is as follows: 

1s² 2s² 2p⁶ 3s² 3p⁵.

To represent the valence electrons, we inspect the outermost energy shells and in this case, we shall take the third shell (3s² 3p⁵). Hence chlorine has 7 valence electrons.

So the answer of “what is the valence electron of Cl?” can now be solved as: 

It has seven and they are located on the third energy level.

Does Chlorine Have 7 or 8 Valence Electrons?

Doesn’t this confuse a lot of people? 

Rather, Does chlorine have 7 or 8 valence electrons? 

It only has 7, as the answer deep down clarifies.

The octet rule, which declares that atoms are most stable when having 8 electrons in their outer shell, is the source of the confusion.  

As I explained earlier, Chlorine desires 1 additional electron in order to achieve this stable configuration, commonly through ionic or covalent bonds.  

Thus, chlorine grapples with having only 7 electrons while seeking 8 valence electrons to achieve stability.  

Is Chlorine a Valency 7 or 1?  

Now, moving on:  

The dilemma becomes, “Is chlorine a valency 7 or 1?”  

This highlights an important aspect that many people fail to capture which is the distinction between valence electrons and valency.  

• Chlorine has 7 valence electrons and a valency of 1.  
• The explanation is simple; valence electrons are classified as the electrons present in the outermost shell. In this particular case Chlorine has 7.  
• Conversely, a valency refers to the number of electrons an atom must gain, lose, or share to achieve a complete outer shell. Chlorine typically gains 1.  
• Chlorine has 7 valence electrons, but its max valency is 1.  

“The reason being, it only needs one more electron to achieve its octet.”  

Point being in most compounds like Sodium Chloride (NaCl) it gains one electron from Sodium (Na).  

Let’s further elaborate as to “Why does Chlorine have 7 valence electrons but not 7 for valency?”

Why is the number of valence electrons assigned to chlorine 7, yet its valency is not 7?

Chlorine is another element that follows the octet rule. The outer shell seeks 8 electrons for stability; therefore, it:

• Prefers to gain one electron when ionic bonding occurs.
• Or share one electron when covalent bonding occurs.

Chlorine’s most stable covalent form is diatomic, Cl=Cl. Valency is defined as the number of bonds an element can form. Chlorine, therefore, has a valency of 1. This is because it can increase the bonds it forms by only needing one more electron.

If it did possess such a valency of seven, this would mean chlorine would have to give away 7 electrons, which would not be feasible in practicality for a non-metal like chlorine.

Can Cl Have 14 Valence Electrons?

Yes, it does sound extreme but it’s a line worth a thought.

“Can Cl have 14 valence electrons?”

Of course, no chlorine does not hold true to resting with 14 valence electrons. Yet, in some expanded octet compounds like ClF₃ or ClO₄⁻, chlorine is able to share more than 8 electrons.

This still holds true because chlorine belongs to the third period, meaning he has access to empty d-orbitals which enables him to accommodate more than 8 electrons.

But in such scenarios too, it doesn’t ‘have’ 14 valence electrons in the conventional way. It is capable of exceeding four bonds which can mean accommodating 12 or more outer shell electrons. These, however, are not electrons that belong to the atom but shared electrons.  

So, in a nutshell:  

Cl can expand on its valence shell and extend it, albeit not meaning that it naturally has 14 valence electrons.  

How to Calculate Valence Electrons?  

“How to find out the number of valence electrons?”  

If armed with a periodic table, identifying valence electrons can be quite easy.  

Steps:  

• Look for the element’s group number.  
• In the case of the main group elements (Groups 1–2 and 13–18), the number of valence electrons = the last digit of the group number.  

In case of chlorine:  

It’s in Group 17 (or Group VIIA)  

Therefore, it has 7 valence electrons  

One can also use electron configuration:  

Chlorine: 1s² 2s² 2p⁶ 3s² 3p⁵  

The outer shell is 3s² 3p⁵ = 7 valence electrons.  

What Element Has 7 Valence Electrons in Its 3rd Energy Level?  

This leads us back to chlorine.  

The question: “What element has 7 valence electrons in its 3rd energy level?”  

The answer is also chlorine. Cl has 7 electrons in the outermost shell which make it super reactive and even more prone to forming stable bonds. It’s the electrons in the third shell that are participating in the chemical bonds.

Other halogens, such as bromine, follow this trend as well, but at higher energy levels.

What is the Rule of 8 Valence Electrons?

I presume you’ve heard the term “octet rule,” which is synonymous with the rule of 8 valence electrons.

“ “What most people refer to as ‘the rule of 8 valence electrons’ is: ”

Atoms tend to be the most stable when there are 8 electrons in the outermost shell.

This helps to rationalize:

• The main reason why chlorine gains 1 electron.
• The main reason why sodium loses 1 electron.
• The main reason why carbon will make 4 bonds (to share and complete his octet).
• Chlorine has 7 valence electrons and will form 1 bond (either ionic or covalent) to achieve his octet and get a noble gas configuration like Ar.

Does Chlorine Have 9 Electrons?

This one is a little tricky.

“Chlorine has 9 electrons, right?”

Wrong, a neutral chlorine atom has 17 electrons. It’s not quite 9.

But if the question is about electrons of value, the answer is still no, chlorine has even less: 7.

So let’s clarify:

Shell                           Electrons

1st                           2

2nd                       8

3rd                           7

Total                       17

Chlorine aims to receive 1 more electron which would make the total in the third shell 8, not 9.

Summary: Obtain Summary Answers To Your Critical Questions

Question Answer

Does chlorine have 7 or 8 valence electrons? 

7 

What is the valence electron of Cl? 

7 electrons in the third shell 

Is chlorine a valency 7 or 1? 

Valency is 1 

Which element possesses 7 valence electrons in its 3rd energy level? 

Chlorine 

Can Cl have 14 valence electrons? 

Only in certain compounds. 

How to calculate valence electrons? 

Based off of group number or configuration 

Why does chlorine have 7 valence electrons and not a valency of 7? 

It’s easier to gain 1, not to lose 7. 

What is the rule of 8 valence electrons? 

Atoms seek 8 electrons for stability (octet). 

Does chlorine have 9 electrons? 

No, it possesses 17 in total with 7 being valence. 

Final Thoughts 

Chlorine, an element at the center of many chemical reactions, is more valuable than the chlorinated water in swimming pools. Clearing up its valence electrons clarifies confusion around the bonding, reactivity, and behavior of a chemical.

If you are still asking the question “why does chlorine have 7 valence electrons and not a valency of 7” then consider the fact that the former refers to the resource and the latter the action.

Regardless of if you are a student, a scientific passionate, or a simple passerby, these short cuts can help you comprehend the periodic table more easily.