PERIODIC CLASSIFICATION OF THE ELEMENTS

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NAME PER DATE DUEACTIVE LEARNING I N C HEMISTRY E DUCATION"ALICE"CHAPTER 11PERIODICCLASSIFICATIONOF THEELEMENTSThe Periodic TableFamilies of Elements11-1 1997, A.J. Girondi

NOTICE OF RIGHTSAll rights reserved. No part of this document may be reproduced or transmitted in any form by any means,electronic, mechanical, photocopying, or otherwise, without the prior written permission of the author.Copies of this document may be made free of charge for use in public or nonprofit private educationalinstitutions provided that permission is obtained from the author . Please indicate the name and addressof the institution where use is anticipated. 1997 A.J. Girondi, Ph.D.505 Latshmere DriveHarrisburg, PA 17109alicechem@geocities.comWebsite: www.geocities.com/Athens/Oracle/204111-2 1997, A.J. Girondi

SECTION 11.1Introduction to the Periodic TableSo far in your study of chemistry, you have spent most of your time learning about the physicalprinciples which determine the behavior of atoms and molecules. These principles allow us to predict howtemperature, volume, and pressure changes affect gases. They also allow us to solve mass-mass andmass-volume problems using balanced chemical equations. We have also been able to use physicalprinciples to determine atomic masses and chemical formulas using experimental data. However, they donot tell us much about the actual physical and chemical properties of specific chemical substances.A working knowledge of chemistry should include familiarity with the actual properties of chemicalsubstances, as well as an understanding of the laws that govern chemistry. Hopefully, you will begin todevelop this working knowledge as you study this chapter. Each element has its own characteristic set ofproperties that help to distinguish it from other elements. As early as the 1800's, chemists began to lookfor similarities among elements that would allow them to be classified into groups. Early chemists knewthat it would be much easier to study groups of elements rather than each of the elements individually.The task at hand was to develop a way of arranging the elements so they could be groupedaccording to common traits. The Russian chemist Dmitri Mendeleev was the first person to successfullyarrange the elements in an orderly fashion. He arranged the elements in order of increasing atomicmasses in 1869. He then developed a table in which elements with similar chemical properties wereplaced in the same vertical columns. This table was later called the "Periodic Table of the Elements."Mendeleev received a considerable amount of ridicule for his arrangement. His colleaguesjokingly suggested that he try arranging the elements alphabetically! Mendeleev ignored the ridicule andremained committed to his method of arrangement. In the preparation of his table, if the element with thenext highest atomic mass did not fit a particular group, Mendeleev left a blank space on his table andmoved the element up to the next higher group. This resulted in several blank spaces in his table ofelements. He believed that these blank spaces would eventually contain elements that had not beendiscovered yet. He predicted the properties of three of these unknown elements. All three werediscovered in Mendeleev's lifetime and were found to have properties very close to what he hadpredicted! This proved that Mendeleev's arrangement of elements was, indeed, useful.From his studies, Mendeleev concluded that both the chemical and physical properties of theelements vary in a periodic (repeating) fashion with increasing atomic mass. The horizontal rows in thetable are called periods or rows, while the vertical columns are called families or groups. Look at a periodictable now, and distinguish the periods (rows) from the families (groups). Table 11.1 is a copy of theperiodic table which Mendeleev developed in 1871. The periodic table that was developed by Mendeleevenabled chemists to classify knowledge and concentrate their studies on physical and chemical propertiesof groups of elements rather than on each element individually. This arrangement of elements enableschemists to make predictions. These predictions are based on the repeating nature of chemicalproperties.In problem 1 you will be asked to organize a periodic table using some fictional elements. Thefictitious elements and properties are listed in Table 11.2. You are going to enter these elements into theblocks of Table 11.3 Some of the elements have already been filled in for you. As you record eachsymbol on the periodic table, also record its mass in the lower right corner and its formula with chlorine inthe upper left corner of each block. This will make it easier to see the periodic (repeating) properties of theelements. You should use the two rules below when arranging the fictitious elements listed in Table 11.2.RULE 1: Elements are arranged in order of increasing atomic mass from left to right in each row row.RULE 2: Elements in each vertical column all form compounds with similar chemical formulas.11-3 1997, A.J. Girondi

Table 11.1Mendeleev's Periodic Table (1871)11-4 1997, A.J. Girondi

Problem 1. Fictitious elements, atomic masses, and chemical formulas (that show how each elementcombines with chlorine) are given in Table 11.2. On the basis of rule 1 and rule 2 mentioned earlier, youshould now arrange the elements in Table 11.2 in their proper order in the rows and columns of the"Periodic Table of Fictitious Elements" (Table 11.3). Note that some of the fictitious elements havealready been put into Table 11.3 to get you started.Table 11.2List of Hypothetical ElementsElementFormula of Compoundwith ChlorineABDFGHJMNPRSTUZTable 11.3Atomic Mass(g/mole)A 2Cl3(none)DCl3F2Cl3GCl4HCl4(none)MCl3NCl4P 2Cl3RCl2SCl2(none)?ZCl322364453111159493974152?28A Table of Hypothetical ElementsF2Cl3----FFormula with ClJ5Symbol15ZCl3?Z?28SCl2SAtomic Mass4111-5 1997, A.J. Girondi

Look again at the completed blocks in Table 11.3. One space contains the symbol U. Study theother elements in the same column and those in the same row as U. In the spaces below give your bestestimate for the atomic mass of this unknown element and give your prediction of the formula of thecompound it will form with chlorine:Atomic Mass of U is in the range:{1} ; Formula of U with Cl is: {2}SECTION 11.2Development of the Periodic TableIn science we develop models or theories to explain our observations. These models are notperfect, and most have exceptions. Mendeleev's arrangement of elements is no different. WhenMendeleev arranged elements according to similar properties, their atomic masses increased in numberfrom left to right. However, there were exceptions to this rule. Study the periodic table in your classroomor in your notebook.Problem 2. Find two pairs of elements that appear to have their atomic masses reversed from theaccepted increasing order:and ;andThese exceptions cast some doubt on the reliability of using atomic mass as a means of organizing theperiodic table.Henry Moseley found the reason for this apparent exception to Mendeleev's rule. Moseleyaltered the periodic table to base it on atomic numbers rather than on atomic masses, and he restated theperiodic law so that it stated that "the properties of elements are a periodic function of their atomicnumbers." This law has no exceptions. You will learn the reason for this when you study atomic structurein an upcoming chapter.Once again look at a periodic table in your classroom or in your notebook. There are severalthings concerning atomic numbers that are important for you to notice.Problem 3. Answer the questions below .a. How do atomic numbers change as you move through the periodic table?b. Are atomic numbers whole numbers or decimal numbers?c. What element has the smallest atomic number?d. As of June, 1995 there are 111 elements (officially). How many are listed on your table?All matter, from concrete to human skin, iscomposed of either pure elements or elements incombination with each other. The proportions andkinds of elements that are combined determine whatthe particular substance is. Actually, only the first 92elements are considered natural. Those elements withatomic numbers larger than 92 are artificial elements,produced by scientists working in laboratories. Theseelements are referred to as the transuranium elements.When a new element is "discovered," other scientistsmust conduct experiments to confirm the discovery.11-6Table 11.4Naming New mUnnilenniumUnqUnpUnhUnsUnoUne 1997, A.J. Girondi

The discoverer then receives the honor of naming the new element. Precisely who discovered elements104 through 107 is questionable at this time. Russian scientists reported the production of element 104in 1964, element 105 in 1970, element 106 in 1974, and element 107 in 1976. However, Americanscientists have claimed that they produced element 104 in 1968, element 105 in 1970, and element 106in 1974. The Soviet Union has proposed the name Kurchatovium (Ku) for element 107 and Bohrium (Bh)for element 105. The United States has proposed the following names and symbols for elements 104through 109: 104 Rutherfordium (Rf); 105 Hahnium (Ha); 106 Seaborgium (Sg); 107 nielsbohrium (Ns); 108 hassium (Hs); 109 meitnerium (Mt).Until the official names for elements have been agreed upon, it has been suggested that thoseelements be named according to a system which makes names out of combined Greek prefixes. (nil 0;un 1; quad 4; pent 5; hex 6; sept 7; oct 8; enn 9) The names are given a suffix of "ium."The periodic table allows us to study groups of elements as well as individual elements. Onebroad classification of elements is by metals and nonmetals. If we study this further, we find that all metalshave several properties in common that differ significantly from the properties of nonmetals.Problem 4. During 1994 and 1995, scientists in Germany produced elements 110 and 111.them using the system described above, and give their symbols.Namea. 110 name: symbol:b. 111 name: symbol:ACTIVITY 11.3Metals, Nonmetals, & Metalloids - Comparing PropertiesObtain the vials from the materials shelf labeled 11.3. Three of the elements are aluminum,copper, and tin. The remaining 2 elements listed, sulfur and silicon, are classified as a nonmetals. (Siliconis also a metalloid.) Examine each sample for the properties called for in Table 11.5. The melting points ofthe substances may be found in the Handbook of Chemistry and Physics or in a similar reference book.The battery-powered device found with the vials may be used to test the electrical conductivity of eachsample. Simply touch the two wires to one piece of each element. If the device indicates that current isbeing conducted through the element, you should classify the element as having high conductivity. If itdoes not light, classify the substance as having low conductivity. The wires of the device should nottouch each other. "Phase" in Table 11.5 refers to solid, liquid, or gas. "Luster" refers to dull or metallic.Study the information you have collected from Table 11.5 and react to the four statements below.1. Make a general statement about the properties of a metallic substance.11-7 1997, A.J. Girondi

Table 11.5Properties of Selected Metals and NonmetalsElementPhaseLusterConductivityMelting Point onmetal)silicon(nonmetal-metalloid)Propose a hypothesis about why frying pans are usually made of metals while their handles are usuallymade of nonmetals like wood or plastic.The melting point of a substance is related directly to its hardness. Elements with high melting points aregenerally hard substances. With this is mind, list the substances in Table 11.5 from hardest to softest.hardest--- ------softestDo the hardest materials appear to be metals or nonmetals? {3}Locate the "staircase" on the right side of the periodic table. The elements that are located to theleft of this staircase are classified as metals, while those to the right of it are nonmetals.Are most elements metals or nonmetals?{4}Name 3 metals:Name 3 nonmetals:The elements that border the staircase on the periodic table are known as metalloids. Theseelements have some properties that make them resemble metals, but other properties that make themresemble nonmetals. They include the elements just above and just below each step of the staircasestarting with aluminum (#15). A good example is silicon. Silicon is known as a "semiconductor" because itconducts electricity better than nonmetals, but not as good as metals. It is the major component ofcomputer chips.Obtain the sample of silicon from the box of materials for Activity 11.3. While silicon is a metalloid,it falls on the nonmetal side of the staircase. Describe one property of silicon that makes it remind you of ametal:11-8 1997, A.J. Girondi

SECTION 11.4The Modern Periodic TableDividing the elements into metals and nonmetals is only one way in which they are categorized.As mentioned earlier, another way to classify them is by families (or groups) and periods (or rows).Elements such as boron, carbon, and neon are in the same horizontal row and are said to be in the sameperiod. Elements in the same vertical column, such as lithium and sodium, belong to the same family orgroup. To distinguish the families of elements, the families (or groups) have names as well as numbers.Note in Table 11.6 that the families are numbered 1A through 8A, while the periods (rows) are numbered1,2 3, etc.Table 11.6The “A” Families on the Periodic Table8A1A3A2A4A5A6A7A107 108 109 110 111Unh Uns Uno U n e Uun Uuu*Some authors do not consider aluminum (#13) or Astatine (#85) to be metalloids.The families used to be broken up into two subgroups which were labeled the "A" families and the"B" families. The transition elements in the center of the table were included in this system. You probablywill see periodic tables in your classroom or elsewhere that still use this system. However, the mostmodern labeling system now includes 18 families of elements including the transition elements. It isshown in the following partial periodic table (Table 11.7).Some families are often named according to the first element in the family. For example, family 16above is the oxygen family, family 15 is the nitrogen family, family 14 is the carbon family, and family 13 isthe boron family. These families also have other names which are not in common use. Other familieshave commonly-used special names. Family 18 is known as the noble gases, family 17 elements areknown as the halogens, family 1 elements are called the alkalimetals, while family 2 elements are known asthe alkaline-earth metals. See Table 11.8. The metals in the center block of the table are collectivelyknown as the transition metals. The two rows at the bottom of the table (the lanthanide and actinideseries) are collectively known as the rare earth elements. In Table 11.8, write in the "names" of families 13through 16.11-9 1997, A.J. Girondi

Rows 6 and 7 of the periodic table are not shown here (to save space).You have seen that metals have properties that help to distinguish them from nonmetals. In thesame way, each chemical family has a set of characteristic properties. We will be taking a closer look atsome of the properties associated with each chemical family.Problem 5. Refer to Table 11.8 and a periodic table to help you with the following.a. Write the symbols for the alkali metals:b. Write the symbols for the alkaline-earth metals:c. Write the symbols for the halogens:d. Write the symbols for the noble gases:e. Name the elements in group IIIA (or group 13):f. Name the elements in group VA (or group 15):You have been told that the members of a family of elements have similar properties. The alkalimetals, for example, all react with water in the same proportions to form compounds that have similarchemical formulas.Problem 6. The chemical equations below illustrate reactions between a few alkali metals and water.Complete and balance each equation. Note the similarity of the equations for the various family 1Aelements:a. 2 Li 2 HOH ---- b. Rb HOHc. Cs 2 LiOH 1 H2------ RbOH H2HOH------ CsOH H211-10 1997, A.J. Girondi

121A2ATable 11.8Names of Classes and Families of Elements131415163A4A5A6A17187A8A ----- 3 THROUGH 12 ------ ScZntransition metalsTransition MetalsLanthanide SeriesRare-Earth ElementsActinide SeriesACTIVITY 11.5Properties of Alkaline-Earth Element CompoundsOne chemical family that is more easily and safely studied is the alkaline-earth metals. Find thematerials labeled 11.5 on the materials shelf. Because elements in the same families have strong familyresemblances, you can predict the chemical behavior of other family members if you know how one or twofamily members act in a chemical reaction. The experiment presented here will help to illustrate this point.Be sure to wear glasses! Use standard 150 mm test tubes.Procedure:1. Place 5.0 mL of 0.1 M magnesium nitrate, Mg(NO3)2, solution into a test tube. Into a second test tube,place 5.0 mL of 0.1 M calcium nitrate, Ca(NO3)2, solution.2. Add 5.0 mL of 0.1 M sodium carbonate, Na2CO3, solution to each test tube. Stopper and shake bothtubes well. Describe what happens in each tube.3. Strontium, barium, magnesium, and calcium are all members of the same family, the alkaline-earthmetals. Suppose you had solutions of strontium nitrate, Sr(NO 3)2, and barium nitrate, Ba(NO3)2. Predictwhat would happen if you mixed each of these solutions with sodium carbonate, Na2CO3, solution.11-11 1997, A.J. Girondi

4. What knowledge allows you to make the above prediction?5. Test your prediction by repeating the procedure in steps 1 and 2, but this time use 0.1 M strontiumnitrate, Sr(NO3)2, solution and 0.1 M barium nitrate, Ba(NO3)2, solution. Describe the changes in detail.6. Suppose you were given a test tube containing a clear liquid. How could you test it to determine if analkaline-earth metal were in the liquid?7. Wash all tubes and put the materials and solutions back in their proper places.ACTIVITY 11.6The Properties of Halogen CompoundsAnother group of elements that have family resemblances are the halogens. You will observesome of those similarities in this activity. Find the materials labeled 11.6 on the materials shelf. Be sure towear glasses!Since the halogens are a family, they all react in a similar fashion with silver nitrate, AgNO3, to forma solid (precipitate). Each precipitate which forms, however, is slightly different from the others. We will betaking advantage of these differences to try to identify which halogen is present in an "unknown"solution. By comparing the reaction of the unknown halogen to the reactions of the known halogens, it ispossible to identify the unknown as being a compound of bromine, chlorine, or iodine.1. Carry out the reactions outlined in Table 11.9. In each situation, add 1 mL of each halogen solution to 1mL of AgNO3 solution, stopper, and shake each test tube.2. Observe any reaction that occurs, and then add 2 to 3 mL of 6.0 M NH4OH solution, stopper, and shakefor a minute. Observe any change.3. Complete and balance each equation. (The first one has been done for you.) Identify any precipitate.Write your observations such as color of a precipitate, etc. Be certain that your test tubes and otherequipment are clean before you begin any of the combinations listed in Table 11.9.4. Wash and rinse several times with a little distilled water if you have any doubt. Caution: handle AgNO3with care. It can cause harmless, but dark, temporary stains o

broad classification of elements is by metals and nonmetals. If we study this further, we find that all metals have several properties in common that differ significantly from the properties of nonmetals. Problem 4. During 1994 and 1995, scientists in Germany produced elements 110 and 111.

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