Question

In the following pairs of binary compounds determine which one is a molecular substance and which one is an ionic substance. Use the appropriate naming convention (for ionic or molecular substances) to assign a name to each compound: (a) \(\mathrm{TiCl}_{4}\) and \(\mathrm{CaF}_{2}\), (b) \(\mathrm{ClF}_{3}\) and \(\mathrm{VF}_{3}\), (c) \(\mathrm{SbCl}_{5}\) and \(\mathrm{AlF}_{3}\).

Short answer

(a) \(\mathrm{TiCl}_{4}\) is an ionic substance named Titanium(IV) chloride, and \(\mathrm{CaF}_{2}\) is an ionic substance named Calcium fluoride. (b) \(\mathrm{ClF}_{3}\) is a molecular substance named Chlorine trifluoride, and \(\mathrm{VF}_{3}\) is an ionic substance named Vanadium(III) fluoride. (c) \(\mathrm{SbCl}_{5}\) is a molecular substance named Antimony pentachloride, and \(\mathrm{AlF}_{3}\) is an ionic substance named Aluminum fluoride.

Step-by-step solution

Understanding Molecular and Ionic Substances

Ionic substances are formed by a metal and a non-metal element. In an ionic compound, electrons are transferred, generating a positively charged cation and a negatively charged anion. Molecular substances, on the other hand, are composed of only non-metal elements, and the electrons are shared between atoms, forming covalent bonds.

Compound Identification and Naming

Use the periodic table to identify the element types (metal or non-metal) in each compound, and then determine if the compound is ionic or molecular. Once the type is determined, apply the naming conventions for that type of substance. (a) \(\mathrm{TiCl}_{4}\) and \(\mathrm{CaF}_{2}\): - \(\mathrm{TiCl}_{4}\): Ti is titanium (a metal) and Cl is chlorine (a non-metal); it is an ionic substance. - Name: Titanium(IV) chloride (charge on the metal indicated in the roman numeral) - \(\mathrm{CaF}_{2}\): Ca is calcium (a metal) and F is fluorine (a non-metal); it is an ionic substance. - Name: Calcium fluoride (b) \(\mathrm{ClF}_{3}\) and \(\mathrm{VF}_{3}\): - \(\mathrm{ClF}_{3}\): Cl is chlorine (a non-metal) and F is fluorine (a non-metal); it is a molecular substance. - Name: Chlorine trifluoride - \(\mathrm{VF}_{3}\): V is vanadium (a metal) and F is fluorine (a non-metal); it is an ionic substance. - Name: Vanadium(III) fluoride (charge on the metal indicated in the roman numeral) (c) \(\mathrm{SbCl}_{5}\) and \(\mathrm{AlF}_{3}\): - \(\mathrm{SbCl}_{5}\): Sb is antimony (a metalloid) and Cl is chlorine (a non-metal); it can form covalent bonds, so it is a molecular substance. - Name: Antimony pentachloride - \(\mathrm{AlF}_{3}\): Al is aluminum (a metal) and F is fluorine (a non-metal); it is an ionic substance. - Name: Aluminum fluoride

Key concepts

Naming Chemical Compounds

Naming chemical compounds can sometimes feel like learning a new language, but it's all about understanding the rules and putting them into practice. For starters, compounds can be mainly divided into two categories: ionic and molecular.

For ionic compounds, which are composed of metals and non-metals, we typically name the metal first followed by the non-metal. A key point here is that if the metal can form ions with different charges, we specify the charge using Roman numerals. For instance, in "Titanium(IV) chloride," the Roman numeral IV indicates that titanium has a +4 charge. Ionic names tend to lack prefixes.

In contrast, molecular compounds, which are made of non-metals, use prefixes to denote the number of atoms. For example, "Chlorine trifluoride" means that there is one chlorine atom and three fluorine atoms, as indicated by the prefix 'tri-' for three. Understanding these naming conventions helps in identifying and differentiating between compound types.

Ionic Bonds

Ionic bonds form when electrons are completely transferred from one atom to another, resulting in the formation of ions. This typically occurs between metals, which lose electrons, and non-metals, which gain those electrons. The loss of electrons by the metal forms a positively charged ion (cation), such as the calcium ion in calcium fluoride ( CaF_2 ), while the gain of electrons by the non-metal forms a negatively charged ion (anion), like the fluoride ion.

This electron transfer and resultant attraction between oppositely charged ions characterize ionic bonds. They produce substances with high melting and boiling points, due to the strong electrostatic forces holding the ions together. Ionic compounds are generally crystalline solids and can dissolve in water, leading to solutions that conduct electricity.

Covalent Bonds

Covalent bonds occur when two non-metal atoms share electrons to achieve a stable electron configuration, often fulfilling the octet rule. This sharing can involve one or more pairs of electrons. The classic example can be seen in a compound like chlorine trifluoride ( ClF_3 ), where chlorine and fluorine share electrons to form covalent bonds.

Covalent compounds tend to have lower melting and boiling points compared to ionic compounds because the forces between molecules (intermolecular forces) are weaker than the ionic bonds' electrostatic forces. Moreover, they do not conduct electricity when dissolved in water because they do not break into ions. The polarity of covalent bonds can vary depending on the difference in electronegativity between the atoms involved, which influences the molecule's overall polarity and reactivity.