Question

Predict whether each of the following is held together by ionic or covalent bonds: (a) aluminum chloride, \(\mathrm{AlCl}_{3}\) (b) water, \(\mathrm{H}_{2} \mathrm{O}\) (c) sulfur trioxide, \(S O_{3}\) (d) iron(II) sulfate, \(\mathrm{FeSO}_{4}\)

Short answer

(a) Ionic, (b) Covalent, (c) Covalent, (d) Ionic.

Step-by-step solution

Understand Ionic and Covalent Bonds

Ionic bonds form between metals and nonmetals and involve transfer of electrons, leading to formation of charged ions. Covalent bonds form between nonmetals and involve the sharing of electron pairs.

Analyze Aluminum Chloride (AlCl3)

Aluminum is a metal and chlorine is a nonmetal. The bond between them involves the transfer of electrons from Al to Cl, forming ionic bonds. Hence, AlCl_{3} is held together by ionic bonds.

Analyze Water (H2O)

Hydrogen and oxygen are both nonmetals, and they share electrons with each other. Therefore, the bonds in H_{2}O are covalent.

Analyze Sulfur Trioxide (SO3)

Sulfur and oxygen are nonmetals. In SO_{3}, the atoms share electrons, indicating covalent bonding.

Analyze Iron(II) Sulfate (FeSO4)

Iron is a metal, and the sulfate ion contains nonmetals. Thus, the bond between the iron and the sulfate ion involves ion transfer, indicating ionic bonds.

Key concepts

Ionic Bonds

Ionic bonds form when electrons are transferred between atoms, leading to the creation of positive and negative ions. This type of bond usually occurs between metals and nonmetals.

For example, when a metal atom like sodium (Na) loses an electron, it forms a positive ion ( ext{Na}^+), while a nonmetal atom like chlorine (Cl) gains an electron to become a negative ion ( ext{Cl}^-). These oppositely charged ions attract each other, resulting in a strong ionic bond.

Here are a few key characteristics of ionic bonds:

• They usually form crystalline structures in solid state.
• Ionic compounds tend to have high melting and boiling points.
• They are often soluble in water and conduct electricity when dissolved or molten.

Covalent Bonds

Covalent bonds occur when two nonmetals share electron pairs. Unlike ionic bonds, there is no transfer of electrons but rather a mutual sharing that creates a bond.

Consider water ( ext{H}_2 ext{O}), where each hydrogen atom shares an electron with the oxygen atom, completing the outer shell for both elements. This sharing creates a stable balance of attractive and repulsive forces between atoms, forming a covalent bond.

Covalent bonds have several important features:

• They can form single, double, or triple bonds, depending on the number of shared electron pairs.
• Covalent compounds normally have lower melting and boiling points compared to ionic compounds.
• They do not conduct electricity in any state because there are no free-moving charged particles.

Molecular Compounds

Molecular compounds, also known as covalent compounds, are composed of molecules formed by covalent bonds. These compounds are made up of nonmetal atoms bonded together through shared electrons.

Common examples include water ( ext{H}_2 ext{O}) and carbon dioxide ( ext{CO}_2).

Important aspects of molecular compounds are:

• They can exist in gases, liquids, or solids, but are often found as gases or liquids at room temperature.
• The compounds usually have distinct, fixed ratios of atoms forming small, discrete molecules.
• They typically have lower melting and boiling points compared to ionic compounds.
• Molecular compounds are generally not conductive, as they do not have ions to carry charge.

Bonding in Chemistry

Bonding in chemistry refers to the attractive forces holding atoms together to form compounds. Understanding these bonds is crucial to predicting the properties and behaviors of different materials.

Chemists classify bonding mainly into two types: ionic and covalent. Each type of bond has unique characteristics but exists on a spectrum, with polar covalent bonds showcasing properties of both.

To further elaborate:

• Ionic bonds result from the transfer of electrons, forming a lattice structure of ions.
• Covalent bonds involve sharing electrons, resulting in the formation of discrete molecules.
• Understanding hybridization and molecular geometry aids in predicting the shapes and reactivities of molecules.
• Many compounds, like ext{FeSO}_4, exhibit both covalent and ionic character, especially when polyatomic ions are involved.

Grasping the basics of chemical bonding helps unveil a vast range of chemical reactions and material properties, proving fundamental to the study of chemistry.