Question

Identify each compound as an oxide, peroxide, or superoxide. a. MgO b. \(\mathrm{Na}_{2} \mathrm{O}_{2}\) c. \(\mathrm{CsO}_{2}\)

Short answer

Compound a (MgO) is an oxide, compound b (\(\mathrm{Na}_{2} \mathrm{O}_{2}\)) is a peroxide, and compound c (\(\mathrm{CsO}_{2}\)) is a superoxide.

Step-by-step solution

Understanding Oxides

An oxide is a chemical compound that contains at least one oxygen atom and one other element. Metal oxides typically contain an oxygen anion (O^(2-)). When a metal forms a compound with just one oxygen atom, it is termed a simple oxide.

Identifying the Oxide

MgO has one magnesium atom (Mg) and one oxygen atom (O). Since there is only one oxygen atom, it can be identified as a simple oxide.

Understanding Peroxides

Peroxides are a class of compounds where the oxygen atoms are bound together in an O-O group. The common peroxide anion is (O2^(2-)). Peroxides often occur with metals from the s-block of the periodic table (Groups 1 and 2).

Identifying the Peroxide

\(\mathrm{Na}_{2} \mathrm{O}_{2}\) contains two sodium atoms (Na) and two oxygen atoms bound together (O-O). This indicates that it's a peroxide, as it has the (O2^(2-)) anion.

Understanding Superoxides

Superoxides are compounds that contain the superoxide anion (O2^(-)). This anion includes one oxygen molecule (O2) with an extra electron, resulting in a negative charge. They commonly form with alkali metals (excluding lithium).

Identifying the Superoxide

\(\mathrm{CsO}_{2}\) contains one cesium atom (Cs) and a superoxide group (O2). The O2 group in superoxides carries a single negative charge, indicating that \(\mathrm{CsO}_{2}\) is a superoxide.

Key concepts

Oxides

Oxides are quite straightforward compounds that play a significant role in chemistry, especially in reactions involving metals and nonmetals. An oxide consists of one or more oxygen atoms combined with another element.

For instance, magnesium oxide (MgO) is a simple example of an oxide where a single magnesium atom is bonded to a single oxygen atom. This bond produces a neutral compound because the magnesium ion (Mg^(2+)) and the oxygen ion (O^(2-)) balance each other out. In terms of their properties, many oxides are solid at room temperature and can range from being acidic to basic, depending on the nature of the bonded element.

Common Characteristics of Oxides

• Form between metals and oxygen.
• Can be basic, neutral, or acidic.
• Participate in a variety of chemical reactions.

Peroxides

Peroxides are a more complex group of compounds that contain a special O-O bond. This bond connects two oxygen atoms, which collectively hold a (O2^(2-)) charge. The presence of this peroxide anion defines the compound.

Peroxides often form with elements from Group 1 and Group 2 of the periodic table, like sodium in sodium peroxide (Na2O2). Unlike simple oxides, where the oxygen has a (O^(2-)) charge, peroxides divide the extra electrons between the two oxygen atoms. This structure gives peroxides unique properties, like their ability to act as bleaching agents and to decompose into oxides and oxygen gas.

Key Features of Peroxides

• Contain a (O2^(2-)) peroxide anion.
• Typically found with s-block metals.
• Used in industrial processes and as antiseptics.

Superoxides

Superoxides are even more specialized, with each superoxide molecule containing a superscript single negative charge (O2^(-)). These compounds feature an extra electron that gives the superoxide ion its unique chemistry.

Superoxides typically form with alkali metals, such as cesium in cesium superoxide (CsO2), but not with lithium due to its small size and high charge density. These compounds are powerful oxidizing agents due to the presence of the superoxide anion and find uses in applications that require the liberation of oxygen.

Distinguishing Attributes of Superoxides

• Always include the (O2^(-)) superoxide anion.
• Form with alkali metals, except lithium.
• Act as powerful oxidizers and can release oxygen readily.