Video Transcript
Which of the following is an alkaline earth metal? (A) Lithium, (B) rubidium, (C) scandium, (D) strontium, or (E) yttrium.
Alkaline earth metals, as the name implies, are metals. The term alkaline was used to describe these metals because their metal oxides are basic when combined with water. Alkaline earth metals are fairly reactive and are good conductors of electricity. If we knew the properties of the five elements given, we could use these to determine which element is an alkaline earth metal. But we can just as easily determine which is an alkaline earth metal by locating each element on the periodic table.
The elements on the periodic table are arranged such that elements that have similar chemical or electronic properties are found in the same column. We refer to each of these columns as a group. There are 18 columns on the periodic table, so there are 18 groups. Elements of the same group can be referred to by the column number. For example, nitrogen, phosphorus, and arsenic are all group 15 elements. But some groups are given specific names that can be used in addition to or in lieu of the column number. For example, the elements that make up group 18 are called the noble gases. The elements that make up group 17 are called the halogens. All of the elements in group one, apart from hydrogen, are the alkali metals. And all of the elements found in group two are the alkaline earth metals.
So, to determine which of these elements is an alkaline earth metal, we just need to see which of these elements is found in group two of the periodic table. Lithium and rubidium are found in group one of the periodic table. These elements are alkali metals, not alkaline earth metals. Both scandium and yttrium are group three metals. So neither of these elements is an alkaline earth metal. This leaves us with strontium, which is found in group two and is therefore an alkaline earth metal. So, of the five elements given, the alkaline earth metal is answer choice (D) strontium.
