Main Difference – Electrovalent vs Covalent Bond
Electrovalent bond and covalent bond are two types of chemical bonds that are found between atoms of a molecule or a compound. These bonds are helpful in holding atoms together. The formation of these two types of bonds occurs due to the exchange of electrons between two atoms. Electrovalent bond is also called an ionic bond. It is an electrostatic attraction between two atoms. A covalent bond is a result of sharing electrons between two atoms. The main difference between electrovalent and covalent bond is that electrovalent bond is formed when two atoms are in an electrostatic attraction whereas covalent bond is formed when two atoms share their electrons with each other.
Key Areas Covered
1. What is an Electrovalent Bond
– Definition, Explanation of the Formation with Examples
2. What is a Covalent Bond
– Definition, Explanation of the Formation with Examples
3. What are the Similarities Between Electrovalent and Covalent Bond
– Outline of Common Features
4. What is the Difference Between Electrovalent and Covalent Bond
– Comparison of Key Differences
Key Terms: Covalent Bond, Electronegativity, Electrostatic Attraction, Electrovalent Bond, Ionic Bond, Noble Gas
What is an Electrovalent Bond
Electrovalent bond is a type of chemical bond that can be defined as an electrostatic attraction between two atoms. Here, the two atoms either completely lose or completely gain electrons. Therefore, the two atoms become ions. The atom that loses electrons becomes a cation whereas the atom that gains electrons becomes an anion. Therefore, the two atoms build up an attraction force after the electron exchange since they are oppositely charged ions. This attraction force is an electrostatic attraction. It is helpful to hold the two atoms together forming an ionic molecule.
Figure 01: Formation of an Ionic Bond between Sodium (Na) Metal and Chlorine (Cl)
In most occasions, the cation is a metal. This is because metals tend to lose the electrons that are in the outermost orbital rather than gaining a high number of electrons to fill that orbital. Then, the anion will be a nonmetal. This is because nonmetals tend to gain electrons rather than losing all the electrons in their outermost orbital.
This type of bond is called an electrovalent bond because the atoms here do not completely lose or gain electrons since they are in an attraction; they have some degree of covalent bond character. Therefore, this is not a completely ionic bond.
The strength of the ionic bond depends on several factors.
- Size of the Cation – if the cation is very small compared to the anion, the ionic bond is very strong.
- size of the Anion – if the anion is very large compared to the cation, the ionic bond is very strong
- Charge of the Ion – if the charge of the ions are high, the ionic bond will be stronger.
When comparing two different ionic bonds, first one should consider the charge and then the size of ions. These ionic bonds are formed between atoms because they need to stabilize themselves by obtaining the nearest noble gas electron configuration by either removing or obtaining electrons.
This almost complete electron transfer is caused by the high difference in electronegativities of these atoms. Atoms with higher electronegativities will attract electrons more than atoms with lower electronegativities.
What is a Covalent Bond
A covalent bond is a type of chemical bond that is formed due the electron sharing between two atoms. This type of bond is formed between atoms that have a less (than 1.7) or no difference between their electronegativity values. Therefore, most nonmetals form covalent bonds between them. Moreover, the atoms of the same element only form covalent bonds.
A covalent bond has two electrons that are known as bond electron pair. This bond electron pair is formed by the pairing of electrons donated by each atom. Each atom donates one electron per one covalent bond. Therefore, some atoms can donate more than one electron according to the number of their valence electrons. Then these atoms will have more than one covalent bond.
Figure 2: CH4 molecule has four covalent bonds. Therefore, there are four bond electron pairs around Carbon atom.
In order to form a covalent bond, an atom should have at least one unpaired electron in the outermost orbital. Then, this electron can be paired by another electron that is shared by a different atom. According to the orbital where the unpaired electron is present, the formed bond can be either a sigma bond or a pi bond. However, according to the electronegativity of two atoms, the covalent bond can exist as either a polar covalent bond or a nonpolar covalent bond. A polar covalent bond is formed when the difference between two electronegativity values is between 0.4 and 1.7. But if the electronegativity values differ only by 0.4 units, then it is a nonpolar covalent bond.
Similarities Between Electrovalent and Covalent Bond
- Electrovalent and covalent bond are types of chemical bonds.
- Both types are formed due to the exchange of electrons between two or more atoms.
- Both bond types cause two atoms to be held together.
Difference Between Electrovalent and Covalent Bond
Definition
Electrovalent Bond: Electrovalent bond is a type of chemical bond that can be defined as an electrostatic attraction between two atoms.
Covalent Bond: A covalent bond is a type of chemical bond that is formed due to electron sharing between two atoms.
Nature of the Bond
Electrovalent Bond: Electrovalent bond is a type of electrostatic attraction between two atoms.
Covalent Bond: Covalent bond is a direct chemical bond between two atoms.
Electronegativity
Electrovalent Bond: The difference in electronegativity values of the atoms should be higher than 1.7 in order to form an electrovalent bond.
Covalent Bond: The difference in the electronegativity values of the atoms should be lower than 1.7 in order to form a covalent bond.
Ions vs Atoms
Electrovalent Bond: Ions are involved in the formation of electrovalent bonds.
Covalent Bond: Atoms are involved in the formation of covalent bonds.
Conclusion
Electrovalent and covalent bonds are types of chemical bonds. These bonds are formed due to the electron exchange between atoms. One atom can have more than one electrovalent or covalent bonds. The main difference between electrovalent and covalent bond is that electrovalent bond is formed when two atoms are in an electrostatic attraction whereas covalent bond is formed when two atoms share their electrons with each other.
Image Courtesy:
1. “NaF” By Wdcf – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Covalent” By DynaBlast – Created with Inkscape (CC BY-SA 2.5) via Commons Wikimedia
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