Elements from Another Universe: Understanding the Beauty of the Periodic Table

Transcription

1 Elements from Another Universe: Understanding the Beauty of the Periodic Table Learning Objectives: The students will examine the properties of make believe elements, arrange these elements so as to create trends, and design a periodic table that will reflect these trends. Standards: 3.01 Skills: 0, 1, 2, 3, 4, 5, 6 Strand: Safety Precautions: none Science Concepts: Students should be able to recognize the complexity of the periodic table. In addition, they should be able to use the modern periodic table and its trends to predict the properties of elements. Materials: element cards, key to element cards Procedure: 1. Ask students what they know about the modern periodic table. 2. Give students information on Dmitri Mendeleev and his periodic table. 3. Explain to students that they are astronauts who have landed on a planet in another universe, and they must create a periodic table from the newly discovered elements in this universe. 4. Place students in groups of 3 or Give students the attached handout, a set of element cards, and a key to the cards. 6. Allow students to work on their periodic table for as much time as is necessary. Often, it is good to have students spend some time on the first day, and then to come back to the activity the next day. *This activity is wonderful for differentiation. Some students will become frustrated. To prevent their giving up, give them a small hint to help them get started. For other groups that seem to be less challenged, ask them to find more trends than those asked for on the handout. Teacher Notes: When Dmitri Mendeleev designed the first periodic table in 1869, more than sixty elements had already been identified. Mendeleev arranged the known elements by increasing atomic weight, and as he did so, he was convinced that the properties of elements are in periodic dependence upon their atomic weights (Mendeleev, Principles of Chemistry, 1905, Vol. II). This periodic table was the precursor to our modern periodic table.

2 The modern periodic table is an amazingly compact resource, containing a plethora of information about the elements. The table places elements in vertical columns known as groups. Many of these groups have special names. Groups 1, 2, and are known collectively as the representative elements, and these elements have very predictable electron configurations. Group 1 is known more specifically as the alkali metals, named because of their reaction with water to form basic solutions. Group 2 elements are known as the alkaline earth metals. Groups 3-12 are called the transition metals because many of these elements have multiple charges. Group 17 is known as the halogens, which means salt formers. Group 18 elements are called the noble gases, and they are generally unreactive. The periodic table also places the elements in horizontal rows called periods. All of the elements in the same period have the same number of energy levels. The periodic table can also be broken into four different blocks according to how each element s electron configuration ends. Groups 1 and 2 and helium are known as the s-block because their electron configurations end with either s 1 or s 2. Groups 13-18, except helium, are the p-block, and their electron configurations end with p 1 through p 6. The transition metals are known as the d-block because their electron configurations end with d 1 through d 10. Finally, the lanthanides and actinides are known collectively as the f-block as their electron configurations end with f 1 through f 14. Many trends can be seen on the periodic table. Atomic number, the number of protons an atom has, increases going left to right on the periodic table and from top to bottom. Electronegativity, the tendency of an atom to attract electrons, increases going left to right and decreases going top to bottom. Atomic radius decreases going left to right due to the increased attraction of the positively charged nucleus and increases going top to bottom due to the addition of energy levels. Ionization energy, the amount of energy required to remove an electron from the outermost energy level, increases going left to right and decreases going top to bottom. Finally, metallic character decreases going left to right and increases going from top to bottom. Elements from Another Universe: Understanding the Beauty of the Periodic Table You are an astronaut and have landed on a planet in another universe. The crew sets up a space station, and begins exploring the terrain of this planet. You and the other scientists begin collecting samples of elements from this planet. Quickly, you discover that these are not the same elements found in our universe. In order to better understand these elements, the lead scientist has put your group in charge of designing a periodic table for the elements of this newly discovered universe. Questions: 1. Design a periodic table must have at least three trends, each going in two directions (ie. metallic character decreases going right and increases going down). Prepare a

3 diagram of your periodic table that includes just the symbols and the arrangement. 2. Mendeleev was able to predict that new elements would be discovered because his periodic table had gaps. Using your periodic table, identify elements that are missing. Predict the characteristics of each missing element (acid/base character, molar mass, density, combining number, boiling point, melting point, metallic property). 3. Describe the trends for the following characteristics. Use terms such as from top to bottom and from left to right. Note any exceptions to the general trends. Property acid/base character Trend density boiling point melting point metallic property 4. Once you have finished 1-3, get a periodic table from the teacher and determine if your trends fit the Sargent-Welch Periodic Table. Use the information in the following table to create cards according to the diagram below the table: Element Data Symbol Acid/Base? Molar Mass Density Metallic Character Combining Number Boiling Point Melting Point Vt sa nm 1,5, Wa sb m Wi a m 2, Wn b m 1, Wl sb m So wa intermed. 3, St a m 2, Sl wa m 6,5,4,3,

4 Sg sa m 6,3, Su sb m Nr sb m Mt b m 3, Mm a m 3, Ms sa nm 2,3,5, Nt wa m Rf no oxide nm Pr a m 4, Ow sb m Pl sa nm Ri sa nm 1,3,5, Cv a m 2,3, Db sa m 6,5,4,3, By wa nm Cm a m Bu no oxide nm Km b m 2, Kh a m Hb sb m Hv wa intermed. 4, Lg sb m Hr wb m Hh wa intermed. 3, Ha a m Gr a intermed Gg b m 2,3,4, Ur a m Sy a m 4, Sv wa m 5, Vg sa intermed. 2,4, Vh a nm Ad b m 2, At sa m 7,6,4,3, Bo wa lm 3, Ah a m Bd b m Zs a m 5,4,3, Wr sa nm 2,4, Rz a m 4, Sd b m 2, Rm wa intermed Rs b m 2, Sa wa nm 3,5,

5 Fi sb m Hw wa m 7,6,4,2, Jc sb m Di wa m 2,3,4,6, Ec wa m 2,3,4,6,

6 The following is one possible answer: Vh Fi Ah Rm By Ms Bu Rf Ow Wa Cm Gr Sa Wr Ri Hb Nr Pr Zs Sg At Wi Sd St Wh Ha Bo Vg Pl Jc Lg Hr Ur Sv Db Ec Cv Rs Kh Bd Rz Hh Hv Vt Wl Su Nt Sl Hw Di Gg Km Mn Ad Mt Sy So References: Adapted from ChemCom: Chemistry in the Community, 2 nd edition, 1993, p.108. In addition, much of this activity has been designed from activities shared between teachers, and unfortunately the original source is unknown.