Question

Draw Lewis structures for the following ligands: (a) hydroxo; (b) sulfato; (c) oxalato; (d) thiocyanato- \(N\) -.

Short answer

Lewis structures for the given ligands are drawn by understanding the composition of the molecule, its valence electrons and the rules of bonding. For hydroxo, it's a single bond between Hydrogen and Oxygen, with Oxygen carrying 2 lone pairs and an extra electron; for sulfato, there are 4 double bonds between Sulfur and Oxygen atoms, Oxygen carries the 2 extra electrons; for oxalato, there are 4 double bonds between them, with Carbon atoms sharing 4 electrons; for thiocyanato-\(N\), there's a single bond between Carbon and Sulphur, a double bond between Carbon and Nitrogen,with Sulphur carrying 2 lone pairs and the molecule carrying an extra electron due to the \(-\) charge.

Step-by-step solution

Drawing Lewis Structure for Hydroxo

First, write down the composition of Hydroxo. It consists of one Oxygen atom and one Hydrogen atom so it's \(\text{OH}^-\). Hydrogen carries 1 valence electron, Oxygen carries 6. They share 1 electron to form a bond and remaining layer of Oxygen is filled with electrons. The molecule carries 1 extra electron, hence the \(-\) sign.

Drawing Lewis Structure for Sulfato

Sulfato is an ion with the composition \(\text{SO}_4^{2-}\). Sulfur is at the center of the molecule. It carries 6 valence electrons. Oxygen, each carrying 6 valence electrons surround Sulfur and each shares 2 electrons to form double bonds. So, there are 4 double bonds in total. The ion is charged -2, so 2 extra electrons are added to the Oxygens.

Drawing Lewis Structure for Oxalato

Oxalato is a complex ion with the composition \(\text{C}_2\text{O}_4^{2-}\). The molecule consists of 2 Carbon atoms each double bonded to 2 Oxygen atoms. Calculation of valence electrons results in 4 remaining electrons. These electrons are shared between two Carbon atoms forming another double bond.

Drawing Lewis Structure for Thiocyanato-\(N\)

Thiocyanato-\(N\) is an anion with the composition \(\text{SCN}^-\) with Sulphur at one end, Nitrogen on the other and Carbon in between. Carbon double bonds with Nitrogen and single bonds with Sulphur. Remaining 4 electrons of Sulphur form 2 lone pairs. The molecule carries an extra electron due to the \(-\) charge.

Key concepts

Chemical Bonding

Chemical bonding is a fundamental concept in chemistry that explains how atoms combine to form molecules and compounds. It occurs when atoms share, donate, or receive electrons to achieve a stable electron configuration, usually resembling the nearest noble gas. There are several types of chemical bonds, including:

• Covalent Bonds: These form when two atoms share one or more pairs of valence electrons. For instance, in the hydroxo ion (\(\text{OH}^-\)), oxygen and hydrogen share electrons creating a covalent bond.
• Ionic Bonds: This type involves the transfer of electrons from one atom to another, resulting in a bond between oppositely charged ions. Anions like sulfato (\(\text{SO}_4^{2-}\)) often form ionic bonds when they join with cations.
• Coordinate Bonds: A coordinate bond is a type of covalent bond where both bonding electrons come from the same atom. It's significant in complex ion structures like those discussed in this context.

Understanding these bonds helps us predict how different atoms will interact, determining the shape and reactivity of the resulting molecules.

Valence Electrons

Valence electrons are the outermost electrons of an atom and play a crucial role in chemical bonding. They are the electrons involved in forming bonds between atoms. The number of valence electrons determines an element's reactivity and the types of bonds it can form.
For example:

• Oxygen has six valence electrons and often forms two covalent bonds, as it seeks to complete its octet. In solutions like the sulfato ion (\(\text{SO}_4^{2-}\)), oxygen shares electrons in multiple covalent bonds to achieve stability.
• Carbon, with four valence electrons, forms four bonds in different configurations, including double bonds with oxygen in the oxalato ion (\(\text{C}_2\text{O}_4^{2-}\)).
• Understanding the valence electrons helps in drawing Lewis structures - a way to represent molecules showing how the valence electrons are arranged around atoms.

By knowing an element's valence electrons, we can better predict how it will engage in chemical reactions and form compounds.

Complex Ions

Complex ions are charged species consisting of a metal ion at its core surrounded by molecules or anions called ligands. The formation of complex ions involves coordinate covalent bonds where ligands donate a pair of electrons to the metal.
A good example of a complex ion is the oxalato ion (\(\text{C}_2\text{O}_4^{2-}\)), which acts as a ligand in coordination chemistry. This ion can form complex bonds with metals by donating its lone pairs of electrons.

• Complex ions can have different charges, which determine how they interact with other ions or molecules. These charges play a crucial role in the compound's solubility and how it reacts with other chemical species.
• The geometry of complex ions can vary, impacting their chemical behavior and the types of reactions they partake in.

Understanding complex ions is essential in many fields of chemistry, including analytical and inorganic chemistry, where they are used in titrations and various synthesis reactions.

Anion Structures

Anions are negatively charged ions formed when atoms gain additional electrons. These structures are essential in forming larger compounds and often participate in ionic or covalent bonding.
For instance, in the thiocyanato (\(\text{SCN}^-\)) anion structure, electrons are distributed among sulfur, carbon, and nitrogen. Here, sulfur carries lone pairs due to its extra electrons, while the entire molecule carries a negative charge because of the additional electron.

• Anion structures like the sulfato ion (\(\text{SO}_4^{2-}\)) are formed when oxygen atoms bond covalently to a central sulfur atom. The entire ion carries a charge due to extra electrons that complete other oxygen's octet.
• The negative charge of anions affects their interactions with cations, leading to the formation of ionic compounds.
• Understanding anion structures helps in predicting the stability and reactivity of compounds.

Recognizing how anions interact and bond with other elements gives insights into the structure and function of complex chemical compounds.