Question

Identify each compound as ionic or molecular based on its formula or properties. (a) \(\mathrm{Rb}_{2} \mathrm{O}\) (b) \(\mathrm{C}_{6} \mathrm{H}_{12}\) (c) Liquid at room temperature (d) Conducts electricity when molten

Short answer

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

Step-by-step solution

Understand the Composition

Compounds can be classified as ionic if they consist of metals and nonmetals, where electrons are transferred, forming ions. Molecular compounds consist of nonmetals, where electrons are shared between atoms.

Analyze Compound (a)

Given compound: \( \mathrm{Rb}_{2} \mathrm{O} \)- Rb (rubidium) is a metal.- O (oxygen) is a nonmetal.Since the compound is made from a metal and a nonmetal, \( \mathrm{Rb}_{2} \mathrm{O} \) is ionic.

Analyze Compound (b)

Given compound: \( \mathrm{C}_{6} \mathrm{H}_{12} \)- C (carbon) and H (hydrogen) are both nonmetals.Since the compound consists only of nonmetals, \( \mathrm{C}_{6} \mathrm{H}_{12} \) is molecular.

Analyze Property (c)

Property given: Liquid at room temperature. - Molecular compounds often have lower melting points compared to ionic compounds, making them more likely to be liquids at room temperature. Therefore, a compound that is liquid at room temperature is likely molecular.

Analyze Property (d)

Property given: Conducts electricity when molten. - Ionic compounds conduct electricity when molten because the ions are free to move. - Molecular compounds do not conduct electricity when molten as they do not break into ions. Therefore, a compound that conducts electricity when molten is ionic.

Key concepts

Chemical Bonding

Chemical bonding is the force that holds particles together in compounds. There are two main types of chemical bonds you might encounter: ionic bonds and covalent bonds. The difference between them lies in how the atoms achieve stability through the bond.

• Ionic Bonds: Ionic bonds form when electrons are transferred from one atom to another, leading to the creation of charged particles called ions. A metal atom loses electrons to become a positively charged ion, while a non-metal atom gains those electrons to become negatively charged.
• Covalent Bonds: In covalent bonds, atoms share electrons to achieve a full outer shell of electrons, gaining stability.

When you identify the type of bond in a compound, you can predict the properties of the compound, such as its melting point and conductivity.

Ionic Compounds

Ionic compounds are formed when metals and non-metals bond together through ionic bonding. This involves the transfer of electrons and results in the formation of ions.

• Structure: Ionic compounds have a crystalline structure. The strong attractions between positive and negative ions hold them together tightly.
• Properties: These compounds generally have high melting and boiling points due to the strength of the ionic bonds. They are typically solid at room temperature but can conduct electricity when melted or dissolved in water because ions are free to move.
• Example: An example is ext{Rb}_{2} ext{O}, where rubidium (a metal) and oxygen (a non-metal) form an ionic bond. As a result, it has distinct ionic properties.

Ionic compounds are an essential part of chemistry, demonstrating how the transfer of electrons creates electrically charged ions that combine to form new substances.

Molecular Compounds

Molecular compounds, or covalent compounds, consist solely of non-metals bonded together through covalent bonds, where they share pairs of electrons.

• Structure: These compounds exist as discrete molecules. The intermolecular forces holding them together are generally weaker than the forces holding ionic compounds.
• Properties: Molecular compounds typically have lower melting and boiling points compared to ionic compounds. Many molecular compounds are liquids or gases at room temperature, as the forces between individual molecules are relatively weak.
• Example: Consider ext{C}_{6} ext{H}_{12}, which is made of carbon and hydrogen, both nonmetals. The sharing of electrons forms a stable molecule, which is why this compound is molecular.

Molecular compounds highlight how atoms can share electrons to achieve stability, resulting in a diverse range of substances with varied properties.

Properties of Compounds

The properties of compounds are influenced significantly by the types of bonds present within them. These properties help in categorizing and predicting the behavior of compounds under different conditions.

• Ionic Compound Properties:
  • Usually solid at room temperature with high melting points. This is due to the strong attraction between ions.
  • Can conduct electricity in liquid form or when dissolved in water, as ions are free to move.
• Molecular Compound Properties:
  • Usually have lower melting and boiling points, making them more susceptible to being liquids or gases at room temperature.
  • Do not conduct electricity because they do not break into ions; they exist as neutral molecules.

Determining whether a compound is more likely to be ionic or molecular can be as simple as checking its physical state and conductivity properties. This understanding is essential in predicting reactions and behaviors of various compounds in chemistry.