Question

Classify the bonds in the following as ionic, ionic - covalent, covalent - ionic and covalent: \(\mathrm{I}_{2}, \mathrm{LiCl}, \mathrm{Mg} \mathrm{Te}, \mathrm{Cl}_{2} \mathrm{O}, \mathrm{H}_{2} \mathrm{~S}\).

Short answer

The bonds in each compound are as follows: \(\bullet~\) \(\mathrm{I}_{2}\) - Covalent \(\bullet~\) \(\mathrm{LiCl}\) - Ionic \(\bullet~\) \(\mathrm{MgTe}\) - Covalent-Ionic \(\bullet~\) \(\mathrm{Cl}_{2}\mathrm{O}\) - Covalent (Both Cl-O and Cl-Cl bonds) \(\bullet~\) \(\mathrm{H}_{2}\mathrm{S}\) - Covalent (Both H-S and H-H bonds)

Step-by-step solution

Electronegativity Differences

We can use the electronegativity values of each element to calculate the electronegativity difference between those elements forming a bond in a compound. If that difference is: \(\bullet~\) Greater than 1.8, the bond is considered ionic. \(\bullet~\) Between 1.2 and 1.8, the bond is considered ionic - covalent. \(\bullet~\) Between 0.5 and 1.2, the bond is considered covalent - ionic. \(\bullet~\) Less than 0.5, the bond is considered covalent. Now, let's analyze each compound.

\(\mathrm{I}_{2}\) (Iodine) Bond

Since we have two identical atoms (iodine) forming the bond, the electronegativity difference is 0. Therefore, this bond is covalent.

\(\mathrm{LiCl}\) (Lithium Chloride) Bond

The electronegativity values for lithium and chlorine are 0.98 and 3.16, respectively. The electronegativity difference is 3.16 - 0.98 = 2.18, which is greater than 1.8. As a result, this bond is ionic.

\(\mathrm{MgTe}\) (Magnesium Telluride) Bond

The electronegativity values for magnesium and tellurium are 1.31 and 2.1, respectively. The electronegativity difference is 2.1 - 1.31 = 0.79, which is between 0.5 and 1.2. Thus, this bond is covalent - ionic.

\(\mathrm{Cl}_{2}\mathrm{O}\) (Dichlorine Monoxide) Bond

Here, we have two bonds to analyze: Cl-O and Cl-Cl. The electronegativity values for chlorine and oxygen are 3.16 and 3.44, respectively. For the Cl-O bond, the electronegativity difference is 3.44 - 3.16 = 0.28, which is less than 0.5. This bond is covalent. For the Cl-Cl bond, since we have two identical atoms forming the bond, the electronegativity difference is 0. Thus, this bond is also covalent.

\(\mathrm{H}_{2}\mathrm{S}\) (Hydrogen Sulfide) Bond

Here, we have two bonds to analyze: H-S and H-H. The electronegativity values for hydrogen and sulfur are 2.20 and 2.58, respectively. For the H-S bond, the electronegativity difference is 2.58 - 2.20 = 0.38, which is less than 0.5. This bond is covalent. For the H-H bond, since we have two identical atoms forming the bond, the electronegativity difference is 0. Therefore, this bond is also covalent. To summarize, the bonds in each compound are as follows: \(\bullet~\) \(\mathrm{I}_{2}\) - Covalent \(\bullet~\) \(\mathrm{LiCl}\) - Ionic \(\bullet~\) \(\mathrm{MgTe}\) - Covalent-Ionic \(\bullet~\) \(\mathrm{Cl}_{2}\mathrm{O}\) - Covalent (Both Cl-O and Cl-Cl bonds) \(\bullet~\) \(\mathrm{H}_{2}\mathrm{S}\) - Covalent (Both H-S and H-H bonds)

Key concepts

Ionic bond

An ionic bond forms when one atom donates one or more electrons to another atom, creating ions.
This generally occurs between metals and nonmetals.
The metal loses electrons to become a positively charged ion, or cation, while the nonmetal gains electrons to become a negatively charged ion, or anion.
Such bonds are characterized by their high electronegativity difference, typically greater than 1.8.

• An example of an ionic bond is found in lithium chloride (\(\mathrm{LiCl}\)), where lithium donates an electron to chlorine, resulting in strong electrostatic attraction between the \(\mathrm{Li}^+\) and \(\mathrm{Cl}^-\) ions.

Ionic compounds are usually crystalline solids with high melting points and are generally soluble in water.

Covalent bond

Covalent bonding occurs when two atoms share one or more pairs of electrons, aiming to attain a full valence shell.
This type of bonding typically happens between nonmetals.
The shared electrons allow each atom to achieve a stable electron configuration similar to noble gases.

• Examples include the bonds in \(\mathrm{I}_{2}\) and \(\mathrm{Cl}_2 \), where atoms of the same element share electrons equally, resulting in a bond with no partial charges.

Covalently bonded molecules can vary significantly in terms of physical state and solubility.
The bonds they contain can be either polar or nonpolar, depending on the electronegativity disparity.

Ionic-covalent bond

The concept of ionic-covalent or partially ionic-covalent bonds can be a bit complex, as it illustrates a transition between purely covalent and ionic interactions.
These bonds typically have electronegativity differences between 1.2 and 1.8, indicating some electron sharing but also a significant ionic character.
In a sense, they exhibit characteristics of both ionic and covalent bonds.

• These can be seen in some compounds where the constituent elements have intermediate properties between metals and nonmetals.

Understanding these types of bonds requires analyzing both the physical characteristics and the electronegativity differences.

Covalent-ionic bond

Covalent-ionic or polar covalent bonds have characteristics that include features of both covalent and ionic bonds.
Generally formed between elements with electronegativity differences between 0.5 and 1.2.
These bonds involve unequal sharing of electrons, often resulting in partial charges.

• Magnesium telluride (\(\mathrm{MgTe}\)) is an excellent example of a covalent-ionic bond.The electrons are not equally shared, which imparts some ionic character to the bond.

Such bonds often lead to molecules with distinct dipole moments and can affect their solubility and reactivity.

Electronegativity difference

Electronegativity difference between two bonded atoms is a crucial factor in determining the bond type.
This difference quantifies how strongly each atom attracts electrons in a bond.
A large difference often leads to ionic bonds, where electrons are transferred rather than shared.

• For instance, in \(\mathrm{LiCl}\), the electronegativity difference is significant, leading to ionic bonding.
• Conversely, a very low difference results in covalent bonds, like in \(\mathrm{I}_2\), where electrons are shared equally.

Understanding these differences helps predict molecular behavior, reactivity, and physical properties.