Problem 86 - Chemistry and Chemical Reactivity

Question

Name each of the following compounds, and tell which ones are best described as ionic: (a) ClF \(_{3}\) (f) \(\mathrm{OF}_{2}\) (b) \(\mathrm{NCl}_{3}\) (g) \(\mathrm{KI}\) (c) \(\mathrm{SrSO}_{4}\) (h) \(\mathrm{Al}_{2} \mathrm{S}_{3}\) (d) \(\mathrm{Ca}\left(\mathrm{NO}_{3}\right)_{2}\) (i) \(\mathrm{PCl}_{3}\) (e) \(\mathrm{XeF}_{4}\) (j) \(\mathrm{K}_{3} \mathrm{PO}_{4}\)

Step-by-Step Solution

Answer

Ionic compounds: SrSO4, Ca(NO3)2, KI, Al2S3, K3PO4.

Step 1: Naming compound ClF3

The compound ClF3 is named as chlorine trifluoride. This is a molecular compound formed by a combination of a halogen with another halogen, which indicates that the bonds between them are covalent.

Step 2: Naming compound NCl3

The compound NCl3 is named as nitrogen trichloride. Being composed of non-metals (nitrogen and chlorine), it forms covalent bonds and is therefore a covalent compound.

Step 3: Naming compound SrSO4

SrSO4 is named as strontium sulfate. This compound consists of the metal strontium and the polyatomic ion sulfate. The presence of a metal and a polyatomic ion suggests it is ionic.

Step 4: Naming compound Ca(NO3)2

Ca(NO3)2 is named as calcium nitrate. The compound is formed by the metal calcium and the polyatomic ion nitrate, indicating its ionic nature.

Step 5: Naming compound XeF4

XeF4 is named as xenon tetrafluoride. Xenon and fluorine are both nonmetals, forming a molecular covalent compound with covalent bonds.

Step 6: Naming compound OF2

The compound OF2 is named oxygen difluoride. As it is formed between nonmetals (oxygen and fluorine), the nature of this compound is covalent.

Step 7: Naming compound KI

KI is named as potassium iodide. Being composed of the metal potassium and the nonmetal iodine, it forms an ionic compound.

Step 8: Naming compound Al2S3

Al2S3 is named aluminum sulfide. This compound consists of the metal aluminum and the nonmetal sulfur, indicating it is ionic.

Step 9: Naming compound PCl3

The compound PCl3 is named as phosphorus trichloride. It consists of nonmetals and is therefore a covalent compound.

Step 10: Naming compound K3PO4

K3PO4 is named as potassium phosphate. This compound contains the metal potassium and the polyatomic ion phosphate, indicating it is ionic.

Key Concepts

Molecular Compounds

Molecular compounds, also known as covalent compounds, are formed when two or more non-metals share electrons. This sharing of electrons leads to the creation of covalent bonds, which hold the atoms together in the compound. Examples of molecular compounds include ClF\(_3\) (chlorine trifluoride) and \OF\(_2\) (oxygen difluoride).

These compounds tend to have low melting and boiling points compared to ionic compounds. They are usually gases or liquids at room temperature. Additionally, they do not conduct electricity well, as they do not have free-moving charged particles.

Understanding molecular compounds involves looking at how atoms bond and interact to form stable molecules. This is an important foundation for more advanced study in chemical bonding and molecular chemistry.

Covalent Bonds

Covalent bonds are formed when atoms share pairs of electrons. This type of bond occurs primarily between non-metal atoms, allowing them to reach a more stable electronic configuration. In the compounds \ClF\(_3\) (chlorine trifluoride) and \NCl\(_3\) (nitrogen trichloride), covalent bonds hold the molecules together because the involved atoms achieve stability by sharing electrons.

One key feature of covalent bonds is that they can vary in strength. Double and triple covalent bonds are stronger than single bonds, as they involve more shared electrons. The geometries and angles between covalent bonds influence the overall shape and properties of the molecules.

Covalent bonding is crucial for the formation of numerous organic and biochemical compounds. Understanding this type of bond helps in explaining molecular reactivity, structure, and interaction.

Polyatomic Ions

Polyatomic ions are groups of atoms that are covalently bonded but carry an overall charge, behaving as a single ion. These ions are often part of ionic compounds. For example, in \SrSO\(_4\) (strontium sulfate) and \K\(_3\)PO\(_4\) (potassium phosphate), the sulfate \((\text{SO}_4^{2-})\) and phosphate \((\text{PO}_4^{3-})\) ions demonstrate this concept.

Polyatomic ions participate in ionic bonding with other ions to form stable compounds. They are essential in naming and recognizing various ionic compounds in chemistry. Understanding how these ions combine and interact helps explain everything from simple solubility to complex biological functions.

Learning about polyatomic ions also prepares students for understanding more about acid and base chemistry, where many polyatomic ions frequently appear.

Chemical Nomenclature

Chemical nomenclature is the system used to name chemical substances. Accurate and systematic naming allows for clear communication among scientists. There are specific rules for naming compounds, whether they are ionic or covalent.

For covalent compounds, such as \PCl\(_3\) (phosphorus trichloride), prefixes like mono-, di-, tri-, are used to indicate the number of each type of atom present in the compound. In the case of ionic compounds, such as \Ca(NO_3)\(_2\) (calcium nitrate) and \KI (potassium iodide), the metal name is presented first, followed by the non-metal with an "-ide" suffix, or its respective polyatomic ion's name.

A solid grasp of chemical nomenclature is fundamental for understanding and identifying compounds, conducting experiments, and communicating findings in the scientific community.