Question

Identify each of the following compounds as ionic, covalent, or both. Give the correct IUPAC name for each compound. (a) \(\mathrm{Na}_{3} \mathrm{P}\) (b) \(\mathrm{NH}_{4} \mathrm{I}\) (c) \(\mathrm{SO}_{2}\) (d) \(\mathrm{H}_{2} \mathrm{~S}\) (e) \(\mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}\) (f) \(\mathrm{MgO}\)

Short answer

(a) Ionic, Sodium Phosphide; (b) Ionic, Ammonium Iodide; (c) Covalent, Sulfur Dioxide; (d) Covalent, Hydrogen Sulfide; (e) Ionic, Copper(II) Nitrate; (f) Ionic, Magnesium Oxide.

Step-by-step solution

Identify the type of bond

First, determine the type of bond for each compound. Ionic bonds typically form between metals and nonmetals, and covalent bonds form between nonmetals. Compounds containing a polyatomic ion can also be considered ionic.

Name each compound

Use IUPAC naming rules to name each compound. For ionic compounds, name the cation (metal or positive ion) first, followed by the anion (nonmetal or negative ion). For covalent compounds, use prefixes to indicate the number of atoms if necessary and name the elements in the order listed, with an '-ide' suffix on the second element.

Na3P

This is an ionic compound composed of the metal sodium (Na) and the nonmetal phosphorus (P). The correct IUPAC name is sodium phosphide.

NH4I

This is an ionic compound consisting of the ammonium ion (NH4+) and the iodide ion (I-). The correct IUPAC name is ammonium iodide.

SO2

This is a covalent compound formed between two nonmetals, sulfur (S) and oxygen (O). The correct IUPAC name is sulfur dioxide.

H2S

This is a covalent compound comprising two nonmetals, hydrogen (H) and sulfur (S). The correct IUPAC name is hydrogen sulfide.

Cu(NO3)2

This is an ionic compound containing the metal cation copper (Cu) and the polyatomic anion nitrate (NO3-). Since copper can have multiple oxidation states, we specify the oxidation state in the name. The correct IUPAC name is copper(II) nitrate.

MgO

This is an ionic compound consisting of the metal magnesium (Mg) and the nonmetal oxygen (O). The correct IUPAC name is magnesium oxide.

Key concepts

Ionic and Covalent Compounds

Understanding the difference between ionic and covalent compounds is crucial in chemistry. Ionic compounds are formed when there is a complete transfer of electrons from one atom to another, typically between metal and nonmetal atoms. This transfer creates ions: atoms that have either lost or gained electrons to achieve a full outer electron shell, resulting in a positively charged cation or a negatively charged anion.

For instance, sodium (Na) transfers an electron to phosphorus (P), forming the ionic compound sodium phosphide ((Na_3P)). The `3` in (Na_3P) indicates that there are three sodium ions for every phosphorus ion in the compound. In contrast, covalent compounds are composed of nonmetal atoms that share electrons to achieve stability in their outer electron shells. An example provided in the exercise is sulfur dioxide ((SO_2)), where sulfur and oxygen share electrons to form a stable molecule.

Recognizing the types of compounds helps in predicting properties such as melting point, electrical conductivity, and solubility. Ionic compounds usually have high melting points and, when dissolved in water, conduct electricity. Covalent compounds, however, often have lower melting points and do not conduct electricity when dissolved because they do not form ions.

IUPAC Naming Rules

The International Union of Pure and Applied Chemistry (IUPAC) establishes guidelines to ensure consistent chemical nomenclature, which simplifies the process of identifying compounds. For ionic compounds, the naming convention is straightforward: the name of the metal (cation) comes first, followed by the name of the nonmetal (anion) with its ending changed to '-ide.' In cases of polyatomic ions or transition metals with varying positive charges, additional rules apply.

For example, the ammonium ion is polyatomic, so ammonium iodide is simply named for its components: NH4+ (ammonium) and I- (iodide), hence (NH_4I). With transition metals like copper in copper(II) nitrate, ((Cu(NO_3)_2)), the Roman numeral indicates the oxidation state (II) of copper. Covalent compound naming using IUPAC rules adds prefixes (mono-, di-, tri-, etc.) to indicate the number of atoms. For sulfur dioxide ((SO_2)), 'di-' tells us there are two oxygen atoms.

It's key for students to grasp these rules, as precision in chemical communication can often have safety implications and impacts research integrity.

Chemical Bond Types

A chemical bond is an attraction between atoms that allows the formation of chemical substances containing two or more atoms. The bond is caused by the electromagnetic force between oppositely charged ions in ionic bonds, or through the sharing of electrons as in covalent bonds. These are the two primary types of chemical bonding students encounter.

In addition to ionic and covalent bonds, there is a third type called a metallic bond, which occurs between metal atoms. While not addressed directly in the exercise, understanding metallic bonds is also vital. It entails metal atoms pooling their electrons into a shared 'sea' that gives these substances their characteristic properties like malleability and electrical conductivity.

The bond type significantly affects a compound's properties. Identifying whether a compound like magnesium oxide ((MgO)) is ionic or covalent helps in understanding its behavior, like its high melting point and electrical conductivity when molten – properties indicative of ionic bonding. When studying compounds and their bonds, the arrangement of elements in the periodic table and their electronegativity difference provide valuable clues to the bond type.