Problem 130 - Chemistry and Chemical Reactivity

Question

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

Step-by-Step Solution

Answer

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

Step 1: Naming ClF3

The compound \( \mathrm{ClF}_3 \) consists of chlorine and fluorine. Since both elements are non-metals, the compound is molecular (covalent). It is named chlorine trifluoride.

Step 2: Naming NCl3

\( \mathrm{NCl}_3 \) is composed of nitrogen and chlorine, both of which are non-metals, forming a molecular compound. Its name is nitrogen trichloride.

Step 3: Identifying and Naming SrSO4

\( \mathrm{SrSO}_4 \) contains strontium (a metal) and sulfate (a polyatomic ion), classifying it as an ionic compound. Its name is strontium sulfate.

Step 4: Identifying and Naming Ca(NO3)2

\( \mathrm{Ca(NO}_3)_2 \) includes calcium (a metal) and nitrate (a polyatomic ion), making it an ionic compound. It is called calcium nitrate.

Step 5: Naming XeF4

The compound \( \mathrm{XeF}_4 \) consists of xenon and fluorine, both of which are non-metals, indicating a molecular compound. It is named xenon tetrafluoride.

Step 6: Naming OF2

\( \mathrm{OF}_2 \) is made up of oxygen and fluorine, both non-metals, categorizing it as a molecular compound. Its name is oxygen difluoride.

Step 7: Identifying and Naming KI

\( \mathrm{KI} \) consists of potassium (a metal) and iodine (a non-metal), thus it is an ionic compound. The compound is named potassium iodide.

Step 8: Identifying and Naming Al2S3

\( \mathrm{Al}_2\mathrm{S}_3 \) includes aluminum (a metal) and sulfur (a non-metal), which makes it an ionic compound. It is called aluminum sulfide.

Step 9: Naming PCl3

\( \mathrm{PCl}_3 \) consists of phosphorus and chlorine, both non-metals, making it a molecular compound. It is named phosphorus trichloride.

Step 10: Identifying and Naming K3PO4

\( \mathrm{K}_3\mathrm{PO}_4 \) contains potassium (a metal) and phosphate (a polyatomic ion), meaning it is an ionic compound. It is called potassium phosphate.

Key Concepts

Chemical Nomenclature

Chemical nomenclature is the system used to name chemical substances clearly and accurately. The goal is for each name to convey the composition and structure of the compound. This helps chemists and students understand key details about the compound just by looking at its name.

• Ionic Compounds: These usually consist of a metal and a non-metal or include polyatomic ions. They are named with the metal first followed by the non-metal, which is often modified to end in '-ide'. For example, in potassium iodide (KI), the metal 'potassium' is named first, followed by 'iodide', derived from iodine.
• Molecular Compounds: Formed by non-metals; they are named using prefixes to show the number of each kind of atom. In nitrogen trichloride (\( \text{NCl}_3 \)), the prefix 'tri-' indicates three chlorine atoms.

Learning to name compounds accurately is key in chemistry since it supports effective communication about these substances.

Molecular Compounds

Molecular compounds are composed of molecules formed from only non-metal elements. The bonds within are covalent bonds, meaning the atoms share electrons.

• Because they include only non-metals, molecular compounds have low melting and boiling points compared to ionic compounds.
• The naming uses prefixes like mon-, di-, tri-, etc., to indicate the count of each element. For instance, in xenon tetrafluoride (\( \text{XeF}_4 \)), 'tetra-' indicates four fluorine atoms.
• These compounds can vary in polarity based on their molecular structure and electronegativity of the atoms involved.

Molecular compounds have unique properties that make them essential in various fields, from pharmaceuticals to materials science.

Polyatomic Ions

Polyatomic ions are charged species composed of two or more covalently bonded atoms acting as a single ion. They often form part of ionic compounds but have a unique element of complexity.

• Recognition: Common polyatomic ions include sulfate (\( \text{SO}_4^{2-} \)) and phosphate (\( \text{PO}_4^{3-} \)).
• When naming compounds with polyatomic ions, the ion name remains unchanged, such as in calcium nitrate (\( \text{Ca(NO}_3)_2 \)) where nitrate retains its typical name.
• They appear in various chemical contexts, influencing properties like solubility and reactivity.

Understanding polyatomic ions is critical in predicting the behavior and reactivity of ionic compounds.

Metal and Non-Metal Bonds

Ionic bonds form between metal and non-metal elements, creating ionic compounds. The metal loses electrons to form a positive ion, while the non-metal gains electrons to form a negative ion, resulting in an attraction.

• Characteristics: Ionic compounds typically form crystalline structures, have high melting and boiling points, and conduct electricity when dissolved in water (electrolytes).
• Example Compounds: Potassium iodide (\( \text{KI} \)) and aluminum sulfide (\( \text{Al}_2\text{S}_3 \)) are examples, demonstrating a combination of metal and non-metal ions.
• Recognizing these patterns helps in identifying and understanding a vast array of substances encountered in chemistry.

Grasping how metals and non-metals bond is essential for understanding a wide range of chemical properties and reactions.