MgCl2 is certainly an ionic bond. It is a bond that exists between a metal and a nonmetal. During the formation of magnesium chloride, two outermost electrons are transferred from the magnesium atom to the chlorine atom. In this molecule, magnesium with atomic number 12 is metal whereas chlorine with atomic number 17 is a non-metal.
You should always remember, no matter which molecule is either ionic or covalent atoms always join together for a molecule to achieve stability with minimum energy. As both the atoms magnesium as well as chlorine want to achieve stability, so they join to become a molecule magnesium chloride MgCl2.
Why MgCl2 ionic bond?
Now, the question arises, why MgCl2 don’t share electrons with each other to become a covalent bond? Why there is a transfer of electrons from one atom to another? Here is the answer-
The real purpose of the formation of a molecule is to achieve stability. If there is instability and high energy. then there is no chance of becoming a molecule.
You should always remember, The energy required to remove an electron from an atom is known as ionization and the energy required to accept electrons to complete the outermost shell is known as electron affinity energy.
The reason is we always need to use a very little amount of energy to expel atoms from the magnesium and very little energy to join them to the chlorine atom. Magnesium has very low ionization energy and chlorine has high electron affinity. So, it is easy to become a molecule by losing and gaining electrons
Stability is achieved when the outermost shell of an atom contains 8 atoms. In scientific language, it is called completing an octet.
Electronic configuration of Magnesium is K,L,M=2,8,2. The outermost electrons are two. In each atom of chlorine has seven outermost electrons as it needs one more electron to complete its outermost octet. Its electronic configuration is K,L,M= 2,8,7.
In MgCl2, there is one atom of magnesium and two atoms of chlorine. Magnesium gives two outermost electrons to two chlorine atoms.
Thus, both magnesium and chlorine will final configuration with 8 electrons in the outermost shell. It becomes
- Chlorine=ki LM=2,8,8
You can see the diagram below to understand the representation more accurately.
Now atomic number is equal to number of protons. Protons are positive charge and atomic number of magnesium is 12. So, the number of protons are 12.
The number of electrons in magnesium becomes less as they give them to chlorine. Initially, before donating electrons, the number of electrons is equal to the number of protons.
Magnesium have now more number of protons. It means atom become positive charge.
In the case of chlorine, its atomic number is 17 and the number of protons is also 17. After gaining electrons from the magnesium atom. The number of electrons is now more than the number of protons. The atom becomes negatively charged.
Now, the magnesium atom becomes a positive charge whereas chlorine becomes negatively charged. Just as in the case of magnets positive and negative attract each other, this attraction is a strong electrostatic force that combines atoms together and makes it stronger than the covalent bond. This is how magnesium chloride is an ionic bond not a covalent.
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