Question

The formulas \(\mathrm{MgO}\) and \(\mathrm{CO}\) look very similar. What is the name for each compound? Why do we name them differently?

Short answer

The compound MgO is called magnesium oxide, as it is an ionic compound formed between the metal magnesium and the non-metal oxygen. On the other hand, the compound CO is called carbon monoxide because it is a covalent compound formed between two non-metals, carbon and oxygen. We use prefixes (e.g., mono-, di-, etc.) to indicate the number of atoms of each element in covalent compounds, resulting in the different naming convention compared to ionic compounds.

Step-by-step solution

Identify the elements and bonds in MgO and CO.

In MgO, we have magnesium (Mg) and oxygen (O). Magnesium is a metal, and oxygen is a non-metal. When a metal reacts with a non-metal, they form an ionic bond, in which electrons are transferred from the metal to the non-metal. In CO, we have carbon (C) and oxygen (O). Both carbon and oxygen are non-metals. When two non-metals bond, they form a covalent bond, in which they share electrons.

Naming ionic compounds

To name an ionic compound, we simply write the name of the metal (cation) first and then the name of the non-metal (anion) with its ending changed to "-ide." For MgO, the cation is magnesium, and the anion is oxygen, with its ending changed to oxide. Therefore, the name of the compound MgO is magnesium oxide.

Naming covalent compounds

To name a covalent compound, we use prefixes to indicate the number of atoms of each element in the compound. The prefixes are: mono- (1), di- (2), tri- (3), tetra- (4), penta- (5), and so on. In CO, the compound consists of one atom of carbon and one atom of oxygen. Carbon doesn't require a prefix when it's the first element in a compound, so we can just use the name "carbon" without any prefix. However, for oxygen, we use the prefix "mono-" to indicate there is one atom of oxygen, and change the ending of oxygen to "-ide" for non-metals in such compounds. Therefore, the name of the compound CO is carbon monoxide.

Summary

The compound MgO is called magnesium oxide because it is an ionic compound formed between a metal (magnesium) and a non-metal (oxygen). The compound CO is called carbon monoxide because it is a covalent compound formed between two non-metals (carbon and oxygen), and we use prefixes to indicate the number of atoms of each element in the compound.

Key concepts

Ionic Bonds

Ionic bonds form when there is a chemical reaction between metals and non-metals. These bonds occur because metals tend to lose electrons, while non-metals gain them, resulting in electron transfer. This transfer of electrons creates charged ions.
In an ionic bond, the metal loses one or more electrons, forming a positively charged ion (cation). The non-metal gains these electrons, forming a negatively charged ion (anion). These oppositely charged ions attract each other, leading to the creation of an ionic bond.
Bullet Summary:

• Ionic bonds occur between a metal and a non-metal.
• They involve the transfer of electrons.
• They result in the formation of cations and anions.

Understanding ionic bonds is crucial for naming ionic compounds correctly. Bond formation is a fundamental part of chemical nomenclature, which helps in differentiating substances based on the types of bonds they form.

Covalent Bonds

Covalent bonds form when two non-metals share electrons instead of transferring them. This shared electron pair allows each atom to attain a stable electronic configuration.
Non-metals typically have similar electronegativities, meaning they attract electrons equally well. Because of this, neither atom completely relinquishes an electron but rather shares it. Covalent bonds can be single, double, or triple, depending on the number of shared electron pairs.
Bullet Summary:

• Covalent bonds involve sharing electrons.
• They typically occur between non-metal atoms.
• The shared pairing results in stable molecules.

By understanding the characteristics of covalent bonds, we can apply accurate naming methods for covalent compounds, helping identify them clearly and efficiently.

Compound Naming Rules

Naming chemical compounds correctly is essential for clear communication in science. Different rules apply depending on whether the compound is ionic or covalent.
For ionic compounds, such as magnesium oxide ( parent{MgO} ), the name consists of the metal's name first (magnesium), followed by the non-metal's name with an "-ide" suffix (oxide). This method highlights the metal and indicates its ionic character.
For covalent compounds, in contrast, prefixes indicate the number of atoms present. For example, in carbon monoxide ( parent{CO} ), "mono-" indicates one atom of oxygen. Carbon doesn't use the prefix "mono-" as the first element, but if there were two oxygens, it would be "dioxide." This systematic approach clarifies the compound composition.
Bullet Summary:

• Ionic compounds use the metal and non-metal naming with "-ide."
• Covalent compounds use prefixes like mono-, di-, and tri- to denote atom numbers.
• Proper nomenclature is key for identifying and categorizing compounds.

Mastering these compound naming rules ensures precise communication in chemical contexts.