Which of the following diatomic molecules is joined by a double covalent bond?
A. $O _2$
B. $N _2$
C. $Cl _2$
D. $H _2$
Answer (2)
Oxygen ( O 2 ) forms a double bond ( O = O ) because each oxygen atom needs two more electrons to achieve an octet.
Nitrogen ( N 2 ) forms a triple bond ( N ≡ N ).
Chlorine ( C l 2 ) forms a single bond ( Cl − Cl ).
Hydrogen ( H 2 ) forms a single bond ( H − H ).
Therefore, the diatomic molecule joined by a double covalent bond is O 2 .
Explanation
Problem Analysis We are asked to identify which of the given diatomic molecules is joined by a double covalent bond. To do this, we need to examine the Lewis structures of each molecule and count the number of bonds between the atoms.
Lewis Structures and Bonding Let's analyze each molecule:
Oxygen ( O 2 ) : Oxygen has 6 valence electrons. To achieve an octet, each oxygen atom needs 2 more electrons. Therefore, they share two pairs of electrons, forming a double bond ( O = O ).
Nitrogen ( N 2 ) : Nitrogen has 5 valence electrons. To achieve an octet, each nitrogen atom needs 3 more electrons. Therefore, they share three pairs of electrons, forming a triple bond ( N ≡ N ).
Chlorine ( C l 2 ) : Chlorine has 7 valence electrons. To achieve an octet, each chlorine atom needs 1 more electron. Therefore, they share one pair of electrons, forming a single bond ( Cl − Cl ).
Hydrogen ( H 2 ) : Hydrogen has 1 valence electron. To achieve a duet (stable configuration), each hydrogen atom needs 1 more electron. Therefore, they share one pair of electrons, forming a single bond ( H − H ).
Conclusion From the analysis above, we can see that oxygen ( O 2 ) is joined by a double covalent bond.
Examples
Understanding the types of covalent bonds is crucial in many real-world applications. For example, the properties of materials like polymers and plastics are heavily influenced by the types of bonds between their constituent atoms. A double bond, like the one in O 2 , is stronger and shorter than a single bond, affecting the molecule's reactivity and stability. In the field of drug design, understanding the bonding characteristics of molecules helps in creating drugs that interact effectively with specific biological targets. Similarly, in materials science, engineers can tailor the properties of materials by manipulating the types of chemical bonds present.
The diatomic molecule that is joined by a double covalent bond is O 2 . This double bond occurs because each oxygen atom shares two pairs of electrons to achieve a stable octet configuration. Other molecules listed form either single or triple bonds instead.
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