November 1st - Naming Molecular Compounds

This class, we continued our study of chemical nomenclature. Specifically, we learned all about the naming of molecular compounds. A molecular compound is a compound that is formed by non-metal pure substances.

As a quick review, let's go over the 7 diatomic molecules. They are:

Remembering that diatomic molecules are molecules that consist of two atoms of the same element, we can compare them to polyatomic molecules. Polyatomic molecules are molecules consisting of several atoms of the same element. The two that we study are P₄ and S₈. 

To name molecular compounds, we can start by finding the name of the first element in the compound. As an example, let's use NO. Here, the first element is nitrogen. We then find out the name of the second element and add the suffix '-ide'. In that case, the name of the compound would be Nitrogen oxide. It is important to note that we must always capitalize the first letter of the first element in a compound. However, we aren't done yet. We must also add the proper prefixes. Generally, the first element in the compound does not have a prefix if only one atom of the element exists in the compound. In this case, we leave it as it is. However, the last element must carry a prefix to indicate how many atoms of that element exist in the compound. In the formula NO, there is only one atom of oxygen. In that case, it would get the label 'monoxide', which we get by adding 'mono-' and 'oxide'. With that, we get the final name of the compound: Nitrogen monoxide! Here's a video that explains the process of naming molecules quite well:

It is also important to note that hydrogen generally doesn't carry a prefix.

Here are a few of the molecular compounds that we will study this year:

IUPAC Name/Formula

water/H₂O

Hydrogen peroxide/H₂O₂

Ammonia/NH₃

Glucose/C₆H₁₂O₆

Sucrose/C₁₂H₂₂O₁₁

Methane/CH₄

Propane/C₃H₈

Octane/C₈H₁₈

Methanol/CH₃OH

Ethanol/C₂H₅OH

Another topic we covered was the naming of acids and bases. In most cases, compounds containing hydrogen are acids. For example, the compound HNO₃ is known as nitric acid. It is also important to note that hydrogen is always present on the left of the acid's formula unless it is part of a polyatomic group (such as acetic acid; CH₃COOH).

According to the classical system, the suffix '-ic' and the prefix 'hydro-' indicate the components of a specific acid. To differentiate between the two types of acids, we follow these rules: 

• Polyatomic acids, such as H₃PO₄, use the suffix '-ic'. This compound is made up of hydrogen (an element) and phosphate (a polyatomic molecule) to form phosphoric acid. It is not binary (made of only two elements), so it does not use the prefix 'hydro-'.
• Binary acids, such as HCl, use the prefix 'hydro-'. This compound is made up of only two elements, making it binary. We can name this hydrochloric acid. 

To name hydrogen-containing compounds using the IUPAC system, we simply add 'aqueous' before the chemical name. HCl_(aq) would be named 'Aqueous Hydrogen chloride'.

Bases are formed with a cation and hydroxide (OH), which is usually found on the right side of the formula. For example, Al(OH)₃ would be called aluminum hydroxide. Naming bases is quite simple!

 

Here are a few common acids and bases:

Acid Name/Formula:

Hydrochloric acid/HCl

Nitric acid/HNO₃

Sulfuric acid/H₂SO₄

Phosphoric acid/H₃PO₄

Acetic acid/CH₃COOH

Base Name/Formula:

Ammonia/NH₃

_{Posted  by Michael.}