Group 3A Elements: Definition & Properties

Lesson Transcript
Instructor: Julie Zundel

Julie has taught high school Zoology, Biology, Physical Science and Chem Tech. She has a Bachelor of Science in Biology and a Master of Education.

The Group 3A elements don't have a whole lot in common, so we'll examine their unique characteristics in addition to their similarities. This video will explore the properties and uses of elements in this group.

Definition of Group 3A Elements

Have you ever met a family where no one seemed related, a family where everyone is a black sheep? Maybe there was a slight family resemblance, but for the most part they looked and acted very differently? Meet the 3A family, where they look and act very different from one another.

Group 3A includes boron (B), aluminum (Al), gallium (Ga), indium (In), and thallium (Th), and they are located on the middle-right of the periodic table. Groups are the vertical columns on a periodic table that share similar properties. Periodic tables may look a little different, so you might see this group called 3A, 13, or IIIA - all of these are different ways of saying the same thing.

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Properties of Group 3A

The main thing this group has in common are their electrons, specifically their outer-most electrons. The electrons that are farthest away from the center of the atom are called valence electrons, and they help determine who the element can bond with and how the element behaves. Group 3A has three valence electrons.

Most of the elements in this group lose those three valence electrons and get a +3 charge, otherwise known as a +3 oxidation state. Atoms with a positive charge are called cations, so most of these elements become +3 cations. Notice I said 'most;' some of them can also become a +1 cation, so things can get a little tricky, but don't worry, that'll get explained later in the lesson.

Finally, most of the elements in Group 3A form ionic bonds, where valence electrons are transferred from one atom to another, but remember this group is all a little different, so sometimes they can form covalent bonds, where electrons are shared. Boron is the element that typically forms covalent bonds. Let's take a closer look at each element in this group. Just because they don't share a lot of the same properties doesn't mean they aren't interesting!

Boron is the first element in Group 3A, and is the indecisive member of this family of 3A elements. For example, it doesn't know if it wants to be a metal or non-metal so it has properties of both groups and is called a metalloid. Of course, it's not the only metalloid on the periodic table, but it is the only metalloid in this family. If you check out the periodic table, there's a stair-step line of metalloids dividing the periodic table in half: metals on one side and non-metals on the other.

Boron tends to lose its three valence electrons and form a +3 cation. It isn't found in its pure form in nature and tends to bond, or attach, to elements found in the Earth's crust. It can also be found in the form of borax, working hard to clean your dirty clothes. It is also an important nutrient for plants. Of course, there are other uses for boron, but we don't want this indecisive member of this family to hog the spotlight!

The next family member tends to get all of the glory and is the star of the family. No, it's not a famous athlete, successful businessperson, or humanitarian, but you can find it everywhere! In fact, it's the most abundant metal in the Earth's crust, it lines your pan when you make cookies, and it houses your favorite soda. So, who is this useful and popular member of Group 3A? Aluminum! Like most members of the family, aluminum forms a +3 cation, and like boron, it's not found in its pure form in nature.

Every family has a silly member, right? Well the silly element in this group is gallium. Why? It's a liquid at about 86 degrees F. Can you imagine a metal melting at 86 degrees F? There are only four metals that are liquids around room temperature and gallium is the only one that is in Group 3A. This silly property of gallium makes it quite useful.

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