Alkaline Earths (Group 2A Elements): Definition & Properties

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  • 0:03 Definition of Alkaline…
  • 1:32 Properties Alkaline…
  • 4:57 Alkaline Earth Metals…
  • 6:01 Lesson Summary
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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.

Alkaline earth metals can be found running through your blood... and in nuclear fallout! This lesson will examine properties they share and look at how they impact your health.

Defintion of Alkaline Earth Metals

In the late 1950s, scientists started a project called Plowshare, whose goal was to use nuclear bombs to create new elements, mine ores, construct canals, build roads, and generate heat. It might sound crazy now, but some scientists had hopes of widening the Panama Canal with a nuclear blast and even using nuclear blasts to get to gas and oil reserves in the United States.

In preparation for these projects, tests were conducted throughout the United States. The project slowly died, in part because of a study that examined baby teeth. This study found that radioactive strontium was found in exceptionally high levels in people who lived around the areas where the tests had been conducted. Radioactive strontium is a byproduct of nuclear blasts, and since this form of strontium can cause cancer in high levels, the public pushed to stop Plowshare.

Strontium is one of six elements belonging to the alkaline earth metals, or group 2A. Groups are the vertical columns on a periodic table, and group 2A is on the left. Sometimes, group 2A is represented by roman numerals, or IIA.

Periodic Table

Alkaline earth metals include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra). Elements are grouped together because they share similar properties. Now you might be thinking, a radioactive element shares properties with the calcium in my milk?!

Properties Alkaline Earth Metals Share

Yep, the calcium in your milk and radioactive strontium actually have a lot in common. For starters, they have the same number of valence electrons, or the outermost electrons that give elements a lot of their properties. Alkaline earth metals are group 2A, and they have two valence electrons. So calcium and strontium both have two valence electrons. Big deal, you think, as you slowly back away from your milk. Don't worry. Not all strontium is radioactive, and just because calcium and strontium are in the same group doesn't mean the calcium you've been drinking is radioactive!

Due, in part, to those two valence electrons, alkaline earth metals are extremely reactive. This means they want to bond or attach to other elements. Although they aren't as reactive as their neighbors to the left, the alkali metals, they're still pretty reactive. Because they are so reactive, you can't find alkaline earth metals in their pure form in nature.

For example, calcium combines with carbon and oxygen forming calcium carbonate, which is considered the most common compound on earth. Not only does it make up 7% of the earth's crust, but it also makes up coral, eggshells, and seashells.

This reactivity holds true for other alkaline earth metals. Magnesium combines with oxygen, forming magnesium oxide, which is the second most abundant compound in the earth's crust. You may be noticing a theme here with the earth's crust. In fact, all of the alkaline earth metals can be found in the earth's crust. One of the other groups of elements, the alkali metals, has a name that sounds very similar. In order to keep them straight, remember earth's crust and alkaline earth metals go together.

I know you get the general idea; alkaline earth metals combine with other elements, but I have to share one more, and it's a beauty! Beryllium combines with aluminum, oxygen, and silicon to form beryl, which can come in many forms, including the sought after gemstone, emerald.

Let's get back to those valence electrons. Alkaline earth metals desperately want to get rid of their two valence electrons. This is achieved by giving them away to other elements. Electrons have a negative charge, and when alkaline earth metals give them away, they become a cation, or an atom with a positive charge - specifically a +2 charge. Forming a +2 cation is yet another property all alkaline earth metals share! Being a +2 cation helps determine who alkaline earth metals can bond with - just like all of the elements beryllium combined with to make an emerald or all of the elements calcium combined with to make sea shells.

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