Why Chemical Reaction Took Place

Why Chemical Reaction Took Place

Chemical Reactions
In previous session, we learned about chemical reactions & different signs that represent the ongoing chemical reactions. In this session, we will go in depth to understand the reasons because of which a chemical reaction between different elements or compounds happens.

Chemical Reaction


Chemical reaction is a process, by which one or more substances undergo a chemical change to produce one or more different substances. It means, whenever any process occurred in which one or more substances (which are considered as reactants) take part and they allowed to produce one or more different substances (called as products). Such kind of process is considered as chemical reaction.

Reactants → Products

Why chemical reaction took place?


Every element, atom or compound have their electronic configuration based on their atomic number. This electronic configuration defines their chemical stability, which also defines its chemical behavior and physical & chemical properties. Every element always tries to become more stable in its nature. Stability can be achieved by completing its electronic orbital. Because, elements with complete orbital are more stable as compared to incomplete orbital. Due to this reason elements, atoms or compounds take part in chemical reaction.

To complete their orbital, atoms need to follow Octet Rule.

Octet Rule – Atoms are allowed to lose electrons, to gain electrons, or to share electrons in order to have a full valence shell of 8 electrons. Octet means eight so we can say that, Eight electrons.

This rule is generally applicable for most of the elements electronic configuration.
So, to achieve more stability, atoms are allowed to take part in chemical reaction.

Lose and Gain of Electrons


  • Sodium (Na) and Chlorine (Cl) combination form Sodium Chloride (NaCl)

Here, we have two atoms one is of Sodium (Na) and one is of Chlorine (Cl).

    • Atomic Number of Sodium is 11.
    • Electronic Configuration of sodium is 2, 8, 1
    • It means the outermost orbital Sodium, have only one valence electron.

    • Atomic Number of Chlorine is 17.
    • Electronic Configuration of Chlorine is 2, 8, 7.
    • In Chlorine, outermost orbital have 7 valence electrons.
Lose and Gain of Sodium and Chlorine
Lose and Gain of Sodium and Chlorine

Here, both Sodium and Chlorine, does not have a complete orbital fulfilled with the valence electrons. So that is why they are allowed to take apart in reaction. They are very active in nature. To gain stability, they need to lose or gain electron from their outermost orbital to become stable in nature.

Sodium have only one electron in the outer most orbital and itself is metallic in nature. That’s why sodium can lose the electron present in its outermost orbital and give to Chlorine element. After giving one electron its complete outermost orbital gets neutralized and its second orbit has become its outermost orbital which is full with valance electrons.

Chlorine requires to gain one electrons to fulfill its outer orbital. Chlorine gains one electron from the sodium & chlorine outermost orbital also get fulfilled with eight electrons. So, this reaction happens in which one element lose electron and another element gain electron, then both elements outer orbital is completely fulfilled. Now, both elements get more stable structure.

After giving one electron, Sodium get converted into Sodium ion (Na+) because it’s giving electrons so it’s got a positive charge and become a electro-positive element. Chlorine after taking one electron gets negative charge converted into Chloride ion (Cl­).

Sharing of Electrons

  • Two Chlorine (Cl) atoms makes Chlorine Compound (Cl2)

As seen in previous example, Chlorine has 7 electrons in its outermost orbital.

Chlorine atoms - Sharing of Electrons
Chlorine atoms - Sharing of Electrons

Chlorine is non-metallic in nature and are allowed to share electrons while they are reacting with another non-metallic element. Here, Chlorine is not giving or taking electrons because they are electro-negative in nature.

Because they both have a one un-pair valence electron, they both need only 1-1 electron in their outermost orbital. So they are allowed to share these unpaired electrons with each other to fulfill their orbital with 8 electrons.

As shown in the diagram, their un-pair electron get combined together and their outermost shell of both atoms joined together. Such processes is consider as sharing of electron in which two atoms of any element allowed to take part in reaction and they share their electron and fulfill their orbital with eight electrons.

  •   Two Hydrogen (H) and Oxygen (O) atoms makes Water (H2O)

We have three atoms two is of Hydrogen (H) and one is of Oxygen (O).

    • Atomic Number of Hydrogen is 1.
    • Electronic Configuration of Hydrogen is 1
    • It means the outermost orbital of Hydrogen, have only one valence electron.
    • Atomic Number of Oxygen is 8.
    • Electronic Configuration of Oxygen is 2, 6.
    • In Oxygen, outermost orbital have 6 valence electrons.
Hydrogen and Oxygen atom - Sharing of Electrons
Hydrogen and Oxygen atom - Sharing of Electrons

Hydrogen need one more electron to complete its outermost orbital and Oxygen needs 2 more electrons to fulfill the outermost orbital.

Because, Hydrogen have 1-1 electron, taking part for sharing of electron to combined with the Oxygen. 2 Hydrogen atoms gets combined with un-pair electrons of Oxygen.

So, here by the sharing of electron also, the elements allowed to fulfill the orbital with electrons.

This kind of processes occurred in chemical reaction in which atoms can lose or gain electrons from their outermost orbital. Also, elements are allowed to share their electrons between each other to become more stable.

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