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Lesson 13 The Periodic Table of Elements By PresenterMedia.com •The Periodic Table of Elements • During this lesson, you will see many things that you have seen before. • So, •I we will take a different approach. will ask a question. • You find the answer and write it. • Have your PTE handy. • Ready? •Who is Dmitri Mendeleev? • He was a Russian teacher who found a way to organize the elements. • He wrote each element’s name and properties on a separate card and found a pattern used to classify them. • It is not exactly what we use today, but he created the first PTE. •How are the elements on the PTE arranged? • Mendeleev arranged them by their atomic masses. • When he did this, he saw that many elements in the same columns had similar properties. • However, some did not fit right. • Today, they are arranged by their atomic number. •What are the horizontal rows called? • Each horizontal row is called a period, thus the name periodic table of elements. • The 7. periods are numbered 1 to • Elements in each period increase in atomic number moving across the row from left to right. •What are the vertical columns called? • They are called a group or chemical family. • Groups are numbered from 1 to 18. • Elements in the same group have similar chemical properties. • Their properties are similar because all the elements in a group have the same number of valence electrons. •What are valence electrons? • Valence electrons are the electrons in the outermost energy level. • The number and arrangement of valence electrons tells how atoms of one element will combine with atoms of other elements to form compounds. •Which elements are the main group elements? • Groups 1 and 2 and 13-18 are the main group elements. •What are groups 3-12 called and why? •They are the transition elements. •They include the transition metals, which are generally hard solids with high melting points. •Many transition metals change color when they lose electrons and become charged. •Which groups have how many valence electrons? • Group 1 has one valence electron. • Group • So 2 has two. on and so forth. • This is true for the main group elements. •Where on the PTE are the metals, gases, non-metals, alkali metals, etc.? •With the exception of hydrogen, the elements on the left side of the PTE are metals. •The elements on the right side are nonmetals. •What are properties of metals? • Metals• Are solid at room temperatureexcept for Mercury, which is a liquid • Are malleable and ductile, which means they can be shaped and drawn into wire form • Have luster • Have high conductivity for electricity and heat • Tend to lose electrons in chemical reactions •What are the properties of nonmetals? • Nonmetals• Are mostly gases while others are solid or liquid at room temperature • Are brittle when they are solid • Most are dull in solid form • Are poor conductors of electricity and heat • Tend to gain electrons in chemical reactions •What is reactivity in relation to electrons? • Reactivity is how likely an element is to form compounds with other elements. • The most chemically active metals are in Group 1, the alkali metals. • They have one valence electron that allows them to easily combine with nonmetals. •What are the alkaline earth metals? • • • The alkaline earth metals are the elements in Group 2. They are highly reactive but are slightly less reactive and harder than the Group 1 metals. The reactivity of both Group 1 and 2 metals increases with increasing atomic number. •What is the jagged line on the PTE for? • • • • That line is there to designate the are between the metals and nonmetals. Elements found there are called metalloids. They have properties of both metals and nonmetals. Boron and silicon are both metalloids. •What are the halogens? • • • • • The halogens are the nonmetals in Group 17. They are the most reactive nonmetals Reactivity in nonmetals increases as atomic number deceases, so fluorine is the most reactive nonmetal. Astatine is the least reactive. The halogens react with the alkali metals to form salts. Elements in the halogen family exist in all three states of matter. Fl and Cl are gases, Br and I are liquids, and I and At are solids. •What are the noble gases? • • • • • • The noble gases are the last column-Group 18. They are also known as the inert gases. They are the least reactive elements because they have eight valence electrons, and all elements want to have eight. Originally, they were thought to be unable to react chemically. In 1962, however, a compound containing xenon and fluorine was made. Most noble gases only form compounds under extreme conditions.