The key difference between electrovalency and covalency is that the electrovalency is the number of electrons that an atom either gains or losses in forming an ion whereas covalency is the number of electrons that an atom can share with another atom.
Although the terms electrovalency and covalency sounds similar, they are different from each other according to their definitions. Mainly, the electrovalency explains the formation of an ion whereas the covalency explains the formation of a covalent bond.
CONTENTS
1. Overview and Key Difference
2. What is Electrovalency
3. What is Covalency
4. Side by Side Comparison – Electrovalency vs Covalency in Tabular Form
5. Summary
What is Electrovalency?
Electrovalency is the number of electrons gained or lost during the formation of an ion from that atom. Therefore, it refers to the number of electrons that an atom either gains or losses when forming an electrovalent bond, we call it an ionic bond. according to this explanation, it gives the net electrical charge on an ion. Moreover, if an atom loses electrons when forming an ionic bond indicates a positive electrovalency while if an atom gains electrons when forming an ionic bond, it indicates that the atom has a negative electrovalency. The compounds with atoms having an electrovalency are ionic compounds.
Figure 01: Formation of an Ionic Bond
For example, let us consider the formation of sodium chloride (NaCl). There, the sodium atom loses one electron; thus it has a positive electrovalency. The chlorine atom gains that electron. Thus, it has a negative electrovalency. However, since the number of electrons that are either lost or gained is one, the electrovalency of sodium (or chlorine) is one. We should give the electrovalency with the appropriate sigh in order to indicate whether it is a positive or negative electrovalency.
- Sodium = positive electrovalency sodium can be given as +1.
- Chlorine = negative electrovalency of chlorine can be given as -1.
What is Covalency?
Covalency is the maximum number of electrons that it can share with another atom. Therefore, it indicates the maximum number of covalent bonds that an atom can form using its empty orbitals. The value of this parameter depends on the number of valence electrons of an atom and the number of empty orbitals present in an atom.
For example, a hydrogen atom has only one electron; thus, it can share one electron with another atom. Therefore, the covalency of hydrogen is 1. Unlike in electrovalency, we do not need plus or minus signs because there is no loss or gain of electrons; only the electrons are being shared with each other.
Figure 02: Formation of a Covalent Bond
As we mentioned above, not only the number of valence electrons but also the number of empty orbitals of an atom is important in determining the covalency. For example, if we consider carbon as an example, it has 4 electrons in the outermost electron shell. There, it has the 2s22p2 electron configuration. Hence, there is an empty 2p orbital. Therefore, the two paired electrons in the 2s orbital can separate, and one electron gets included in the empty 2p orbital. Then there are 4 unpaired electrons. Carbon can share all four electrons with another atom. Hence, the covalency of becomes 4. This is because when we write the electron configuration of carbon, we see there are only 2 unpaired electrons, so we think the covalency of carbon is 2 when actually it is 4.
What is the Difference Between Electrovalency and Covalency?
Electrovalency is the number of electrons gained or lost during the formation of an ion from that atom. It explains the formation of an ionic bond. Moreover, the compounds having atoms with this parameter are ionic compounds. Covalency, on the other hand, is the maximum number of electrons that it can share with another atom. It explains the formation of a covalent bond. In addition, the compounds having atoms with a covalency are covalent compounds.
The below infographic presents the difference between electrovalency and covalency in tabular form.
Summary – Electrovalency vs Covalency
Though the terms electrovalency and covalency sounds similar, they have distinct definitions and characteristics. The difference between electrovalency and covalency is that the electrovalency is the number of electrons that an atom either gains or losses in forming an ion whereas the covalency is the number of electrons that an atom can share with another atom.
Reference:
1. “2. Elementary Idea of Bonding.” Role of PH in Everyday Life Chemistry. Available here
2. “Chemistry-Covalency and Molecular Structures.” Biology-Nervous System-Response Time Research. Available here
Image Courtesy:
1.”IonicBondingRH11″By Rhannosh – Own work, (CC BY-SA 3.0) via Commons Wikimedia
2.”Covalent bond fluorine”By Jacek FH – Own work, (CC BY-SA 3.0) via Commons Wikimedia
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