Question

Each of the following compounds is incorrectly named. What is wrong with each name, and what is the correct name for each compound? a. \(\mathrm{FeCl}_{3},\) iron chloride b. \(\mathrm{NO}_{2},\) nitrogen(IV) oxide c. \(\mathrm{CaO},\) calcium(II) monoxide d. \(\mathrm{Al}_{2} \mathrm{S}_{3},\) dialuminum trisulfide e. \(\mathrm{Mg}\left(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}\right)_{2},\) manganese diacetate f. \(\mathrm{FePO}_{4},\) iron(II) phosphide g. \(\mathrm{P}_{2} \mathrm{S}_{5},\) phosphorus sulfide h. \(\mathrm{Na}_{2} \mathrm{O}_{2},\) sodium oxide

Short answer

a. The correct name is "iron(III) chloride." b. The correct name is "nitrogen(IV) dioxide." c. The correct name is "calcium oxide." d. The correct name is "aluminum sulfide." e. The correct name is "magnesium diacetate." f. The correct name is "iron(III) phosphate." g. The correct name is "diphosphorus pentasulfide." h. The correct name is "sodium peroxide."

Step-by-step solution

a. Correcting the name of \(\mathrm{FeCl}_3\)

The given name is "iron chloride." However, due to the presence of iron, a transition metal that can have multiple oxidation states, the correct name should include the oxidation state of iron in this compound. Since there are three chloride (Cl) ions, each with a charge of -1, the charge on iron must be +3. Therefore, the correct name for this compound is "iron(III) chloride."

b. Correcting the name of \(\mathrm{NO}_2\)

The given name is "nitrogen(IV) oxide." However, we should include the subscript 2 for oxygen in the name. The corrected name is "nitrogen(IV) dioxide."

c. Correcting the name of \(\mathrm{CaO}\)

The given name is "calcium(II) monoxide." But since calcium is a Group 2 element with a constant oxidation state, the oxidation state doesn't need to be mentioned in naming the compound. The correct name for this compound is "calcium oxide."

d. Correcting the name of \(\mathrm{Al}_2\mathrm{S}_3\)

The given name is "dialuminum trisulfide." However, the correct IUPAC name for this compound is "aluminum sulfide."

e. Correcting the name of \(\mathrm{Mg}\left(\mathrm{C}_2\mathrm{H}_3\mathrm{O}_2\right)_2\)

The given name is "manganese diacetate." However, the compound contains magnesium, not manganese. The correct name for this compound is "magnesium diacetate."

f. Correcting the name of \(\mathrm{FePO}_4\)

The given name is "iron(II) phosphide." However, we can see that this is actually an ionic compound as it contains a polyatomic anion (phosphate ion). Thus, we need to name it accordingly, and the correct name for this compound is "iron(III) phosphate."

g. Correcting the name of \(\mathrm{P}_2\mathrm{S}_5\)

The given name is "phosphorus sulfide." However, we should include the prefixes for the subscripts of both elements in the name. The corrected name is "diphosphorus pentasulfide."

h. Correcting the name of \(\mathrm{Na}_2\mathrm{O}_2\)

The given name is "sodium oxide." However, as there are two oxygen atoms in the formula, the correct name for this compound is "sodium peroxide."

Key concepts

Oxidation States in Chemistry

Understanding oxidation states is crucial when naming chemical compounds, especially those involving transition metals. An oxidation state is a hypothetical charge that an atom would have if all bonds to atoms of different elements were purely ionic. The oxidation state helps determine how electrons are distributed among the atoms in a compound. For instance, in the compound \(\mathrm{FeCl}_3\), iron must balance the -3 total charge from the three chloride ions. Thus, it assumes an oxidation state of +3, giving it the correct name: "iron(III) chloride."
In compounds where elements can have multiple oxidation states, like transition metals, it's necessary to specify which state the element is in. The Roman numeral in parentheses after the metal's name indicates its oxidation state, helping to avoid ambiguity with compounds that are present in many different forms.
It's important to remember that Group 1 metals always have an oxidation state of +1 and Group 2 metals have +2, which simplifies naming in these cases. Elements like calcium in \(\mathrm{CaO}\) are always named without an oxidation state because they have only one possible oxidation state: "calcium oxide."

Understanding Chemical Compounds

Chemical compounds are substances formed by the chemical combination of two or more elements. They are characterized by a specific ratio of atoms held together by chemical bonds. The naming of chemical compounds follows specific rules set out by the IUPAC, ensuring that each compound's name precisely represents its composition.
For ionic compounds like \(\mathrm{FePO}_4\), the name indicates the types and ratios of ions. "Iron(III) phosphate" shows that the compound contains iron ions with an oxidation state of +3 and phosphate ions. The ending "-ate" or "-ide" in names often indicates the type of ion involved. Polyatomic ions like phosphate (\(\mathrm{PO}_4^{3-}\)) follow specific naming conventions to ensure clarity across varied compound types.
When naming compounds containing nonmetals, prefixes (like "di" for two or "tri" for three) are used to specify the number of atoms, as seen in "diphosphorus pentasulfide" (\(\mathrm{P}_2\mathrm{S}_5\)). These names communicate not just the elements involved, but also their proportions.

Transition Metals and Their Unique Properties

Transition metals, located in the central part of the periodic table, have unique properties. They can exhibit multiple oxidation states and form various ionic and molecular compounds. This is due to their electron configuration - specifically, their partially filled d orbitals.
When naming compounds that include transition metals, it is imperative to specify the oxidation state of the metal. This helps distinguish between the numerous possible compounds that a single element might form with different oxidation states. For example, iron can form \(\mathrm{FeCl}_2\) (iron(II) chloride) and \(\mathrm{FeCl}_3\) (iron(III) chloride) depending on its oxidation state.
Transition metals are known for their ability to form colorful compounds due to electron transfers between d orbitals. Their versatility in forming complex ions also makes them significant in areas ranging from industrial catalysts to biological systems. Understanding their chemistry is key to correctly naming and applying these compounds in different fields.