In 1869, similar discoveries were made by two separate chemists from Russia and Germany, Dmitri Mendeleev and J. Lothar Meyer, respectively. Both men found that the could arrange elements in order of atomic mass, and place them in horizontal rows, with one row underneath the other, such that elements in vertical columns share similar properties. Such a tabular arrangement of the elements in rows and columns, which specifically highlights the common repetition of properties of the elements, is known as the periodic table, which we have discussed before (Ebbing and Gammon 2009).
Important concepts of the periodic table of elements include periods and groups. A period describes any set of elements in any one horizontal row of the periodic table. A group, on the other hand, describes any set of elements in any one vertical columns of the periodic table. If you take a look at any periodic table of elements, the first period contains merely two elements. These are hydrogen (H) and helium (He). The next period is more abundant, with 8 elements, starting with lithium (Li) and ending with neon (Ne). Period four and five have 18 elements each. Period six has 32 elements, but they are not all shown on the same horizontal row. Period seven also has additional elements that are not typically shown on the same horizontal row, but are usually indicated at the bottom of almost any periodic table of elements. The seventh period, however, is not entirely complete (Ebbing and Gammon 2009).
Most examples of the periodic table of elements that you will come across will show the numbering of groups, the vertical columns of the period table of elements. According to the IUPAC convention, groups should be numbered using the numbers 1 to 18. However, in North America, groups are typically numbered using Roman numerals and A’s and B’s. According to this way of doing things, A groups are main-group elements (or representative elements). B groups are transition elements. Inner transition elements are the two rows of elements that can be found at the bottom of the table, which are the extensions of periods six and seven. The first of these rows, corresponding to period six, consists of elements known as the lanthanides. The second of these rows, corresponding to period seven, consists of elements known as the actinides (Ebbing and Gammon 2009).
As mentioned before, elements that belong to the same group, or in other words, those that are within the same vertical column, share some of the same properties. As an example Group IA, or the very first group all the way to the left on any periodic table of elements, contains elements a which are known as alkali metals. These elements are soft metals that react very easily with water. Except, in this group hydrogen is an exception to this property. Another group, Group VIIA or Group 17, consists of elements that are known as halogens, which are highly reactive elements that are the precursors to simple salts (Ebbing and Gammon 2009).
Of particular importance on the periodic table of elements, is the divide between elements that are metals and elements that are nonmetals. You should know that a metal is, in particular, is an element with the property of luster or shine, that is a good conductor of heat and electricity. Almost all metallic elements are solids at room temperature, which is about 20 degrees Celsius. The only exception to this is mercury. As well, these elements may have the properties of malleability, or ability to be hammered into sheets, and ductility, or ability to be drawn into wire. This is fairly relative however, as each element can have these properties to different degrees (Ebbing and Gammon 2009). Most of the elements of the periodic table are metals, and usually, especially with some memorization over time, it is easy to tell where metals are on the table and where nonmetals are.
A little bit more tricky to discern, however, is where metalloids or semimetals are. These elements usually can be found between the metals and semimetals, and they have properties of both metallic and nonmetallic elements. For instance, they can be good semiconductors; this means that when pure, at higher temperatures than room temperature, they become moderately good conductors, but at room temperature, they are poor conductors (Ebbing and Gammon 2009).
Now that we’ve reviewed some basic properties of the periodic table of elements, you should make a good effort to remember some of the information discussed in this post. Note, too, that this is merely the beginning of our discussion of the periodic table of elements. Another major (and fun) part of studying general chemistry is getting to know the trends of the periodic table, which we’ll be going over later on.
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