Periodic Table and Metals Essay

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© 2010 FLVS
Between the metals and the nonmetals on the periodic table lies a small category of elements called the metalloids. A metalloid is a semiconductor that has some characteristics of metals and other characteristics more like nonmetals. The most important property of metalloids is that they are semiconductors, which means that they conduct electricity better than nonmetals, but not as well as metals. This property allows metalloids like silicon and germanium to play an important role in electronic devices like calculators, cell phones, and computers.
Alkali Metals

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The elements in Group 1 of the periodic table are known as the alkali metals. These metals are extremely reactive, reacting with water and with most nonmetals. All of the alkali metals have a silvery appearance and they are soft enough to be cut with a knife. Alkali metals are so reactive that they do not occur in nature as pure elements; they are always found in compounds. Many of these compounds are essential to our lives, including being found in the fluids that fill and surround all of our cells. The metals of this group all have one valence electron, which they give up when they react to form ionic compounds.
Alkaline Earth Metals

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The elements of Group 2 are called the alkaline-earth metals. These metals share similar properties because they each have two electrons in the s sublevel of their outermost energy level. Metals in Group 2 are harder, denser, and stronger than the metals in Group 1.
Although they are less reactive than the Group 1 alkali metals, the alkaline-earth metals are still too reactive to be found as pure elements in nature. Compounds containing alkaline-earth metals are found in the earth’s crust, in sea salts, and in gems and minerals like emerald and aquamarine.
Hydrogen and Helium

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Hydrogen is placed in Group 1 on the periodic table because its electron configuration is 1s1, but it is actually a nonmetal that does not resemble the alkali metals in this group.
Helium has the electron configuration 1s2, meaning it has two valence electrons like the alkaline-earth metals in group 2. So, why is helium found in Group 18 with the noble gases? Like the other noble gases, helium has a full valence of electrons (remember that the first energy level only holds two electrons). There is a special stability related to a full valence, and helium shares this and other properties with the other nonmetals in Group 18.

© 2010 FLVS
The elements in Group 17 are known as the halogens. The halogens are the most reactive of the nonmetals; they react with most metals to form ionic compounds known as salts. As pure elements, the halogens are diatomic molecules.
This means that the halogens bond in pairs, forming compounds such as F2, Cl2, and Br2. As you will learn, the high reactivity of the halogens is based on the presence of seven valence electrons, one electron short of having a full valence. Some of the halogens (F2 and Cl2) are gases at room temperature, while others are liquids (Br2) or solids (I2). The halogens are used in water purification, photography, insecticides, bleaches, plastics, and many other practical applications.
Noble Gases

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Group 18, the group at the far right of the periodic table, contains nonmetals called the noble gases. The first noble gas to be discovered on Earth was argon, which was discovered in 1894 by the English physicists John Williams Strutt and William Ramsay.
Argon makes up one percent of Earth’s atmosphere, but it escaped notice for so long because it does