UP AND ATOM SCIENCE. Overview. ITV Series Eureka #122 Atoms Eureka #123 Electrons

Transcription

1 Overview The periodic table is one of the most important tools of a scientist because it is a classification system used to organize vast amounts of information in a logical, useable, and meaningful way. Much information can be gathered about an element from its position in the periodic table; one can predict physical and chemical properties of a particular element and one can predict what other elements a specific element will react with chemically. Four important facts about an element are given in each square of the Periodic table: atomic number, atomic mass, chemical symbol and name. The number of protons in an element determines its properties. The number at the top of each square in the table tells how many protons the element has; the atomic number is unique to that element; no two elements have the same atomic number. Below the atomic number in the center of the square is the chemical symbol for the element. Below the chemical symbol, the name of the element is spelled out. The number near the bottom of the square is the atomic mass of the element. The atomic mass is made up of the protons and neutrons in each atom. In this lesson, students will explore the most basic particles by examining their chemical make up and reaction to other particles. They will use the Periodic Table, Internet, video and lab experiences to work with and identify various elements and their properties. ITV Series Eureka #122 Atoms Eureka #123 Electrons Learning Objectives Students will be able to: Compare the four states of matter and describe the events that take place during a change of state. Distinguish between physical and chemical changes. Identify the three types of particles found in an atom. Compare and contrast mass number and atomic mass. Plan, create, edit, and format a spreadsheet on subatomic particles. Sketch the electron arrangement of an atom, given its atomic number. Calculate the number of neutrons in an atom based upon the mass number and number of protons for 40 different elements on the spreadsheet. Construct atomic model drawings and use them to make a Periodic Table. Use the Periodic Table to identify properties of specific elements.

2 Distinguish between periods and groups of elements in the Periodic Table. Compare and contrast the elements in a family of the periodic table. Sequence the elements of the periodic table by family and period. Compare and identify elements, compounds, and mixtures. Develop and apply skills in predicting, information gathering, and charting. Develop and apply skills in mathematical calculations, summarizing and recording information. Develop and apply skills in critical analysis of results. Vocabulary Atom Nucleus Electron Neutron Proton Atomic number Mass number Periodic law Compound Chemical formula Chemical bond Materials Per Student: 1 Pencil 1 Thin spiral notebook Colored pencils or markers Scissors String Ruler LAB #1 Per Student Periodic Table Unlined paper Pencil Metric ruler Drawing compass (optional) LAB #2 Per Student Periodic Table Unlined paper Drawing compass (optional) Metric ruler Pencil Per Class Posterboard Per Group Scissors Tape Lab #3 Per Student Samples of elements (Al, Cu, Fe, C, S, I, Sn, Pb, and Zn) Hydrochloric acid Small hammer Chisel or nail Conductivity apparatus Beaker 5 test tubes Dropper Goggles Apron Lab worksheet or Lab Journal Pencil

3 Pre-Viewing Activities Bookmark the following Internet sites prior to class: Interactive Periodic Table Periodic Tables Periodic_Table_of_the_Elements Take students to one of the sites above and demonstrate how to determine the number of protons, neutrons, and electrons in an atom from the Periodic Table. Draw a key to the Periodic Table on the whiteboard with dry erase markers or have transparency ready to put on an overhead projector. Example: 6 atomic number C symbol of element Carbon name of element 12 mass number SAY, The atomic number is the number of protons in the nucleus of the atom. Call on students to find the atomic number (and number of protons) for elements. Using informal oral testing make sure that every student understands how to determine the number of protons; students may be paired with a peer for a cooperative learning variation. (ESL students and mainstreamed special education students might find peer tutoring especially helpful for this study.) Next SAY, An uncharged atom has the same number of electrons as protons. To check for comprehension, ask students the number of electrons in the nucleus of an atom in elements. SAY, The mass number is the total of the protons and neutrons in an atom. Write an example of a mass number on the whiteboard. Beryllium 4 protons + 5neutrons 9 = mass number (atomic mass unit) Write a chart describing the three particles in an atom on the whiteboard or have a transparency of this chart prepared to use on the overhead projector. Chart: PARTICLE RELATIVE MASS CHARGE LOCATION Proton 1 1+ Nucleus Neutron 1 0 Nucleus Electron 0 1- Outside Nucleus (orbiting in energy levels) SAY, Notice that protons and neutrons have the same mass. All the mass of an atom is in the nucleus since protons and neutrons are the biggest particles and are located in the nucleus. The electrons have very little mass

4 (actually it is 1/1836) so we consider the mass of an electron to be 0. As you can see the proton and the electron have opposite charges. The proton is a positively charged particle in the nucleus of the atom. The electron is a negatively charged particle that circles outside the nucleus in paths called energy circles. The neutron, also located in the nucleus, is a particle with no charge. Write the formula on the whiteboard for finding out the number of neutrons in an atom or have a transparency prepared to go on the overhead projector. Remind students: 1) Atomic number = number of protons in atom 2) Same number of electrons as protons Formula to find number of neutrons in an atom: mass number - atomic number = number of neutrons Pose the Questions: What are the particles that make up matter? Are these particles the same in all kinds of matter? Focus for Viewing To give students a specific responsibility while viewing say, Watch the video and compare your answers with the answers featured in the video. You specifically want to know what the smallest particles are and if they are the same in all forms of matter. Viewing Activities Eureka #122 Atoms FAST FORWARD video and be ready to begin immediately following introductory segment. Audio is Our story begins with atoms. Visual is cartoon bird narrator with cartoon tree. To give students a specific responsibility while viewing ASK, How are atoms of pure elements different from the molecules in nonmetals, liquids, and gases? As you watch the video, discover if pure elements have molecules or atoms. BEGIN video. STOP the video at the visual of the cartoon narrator made of Legos and the audio is Be thankful you don t live in a world of Lego. Allow students to list examples of pure elements such as gold, lead, silver, aluminum, copper, and iron. Allow time to discuss atomic characteristics in pure elements. Allow adequate time for interactive class discussion. SAY, What characteristics did you observe in the video for pure elements? Allow students to compare observations made of

5 characteristics. Discuss the rationale for each answer. SAY, Imagine taking a pure sample of an element, such as gold, and cutting it in half. Suppose you cut it in half again and again. You would finally have a piece so tiny that it could not be divided further and still be gold. That piece is called an atom. An atom is the smallest particle of an element that has the properties of that element. What is a model of something? (A means by which scientists try to explain something they cannot see or understand by relating it to something that they do see or understand.) Accept all reasonable responses. SAY, Democritus, a Greek philosopher who lived over 2000 years ago, was the first person to form a model of the atom. His model suggested that all matter has made up of small, indivisible articles. The model of the atom has undergone many modifications since John Dalton proposed a model of an atom in Dalton s model depicted the atom as a solid, indivisible sphere. In 1897, J.J. Thomson, a British physicist, showed that atoms contained negatively charged particles that he called electrons. Thomson s model of the atom showed a positively charged sphere with electrons embedded in it. In 1911, Ernest Rutherford s famous gold foil experiment led to the discovery that the atom consisted of a tiny, densely packed, positively charged core, or nucleus, with electrons orbiting the nucleus at some distance. Most of the atom consisted of empty space. In 1932, James Chadwick, one of Rutherford s students, found evidence of the neutron, the existence of which had been predicted by Rutherford. Show a picture of an atom and SAY, It is difficult to really imagine the size of an atom. The period at the end of this sentence might hold one hundred billion atoms! What particles make up an atom? Allow students to discuss. Accept all reasonable responses. ASK, Can you compare the sizes of the parts of an atom? Allow students to discuss. Accept all reasonable responses. SAY, Imagine an atom is the size of a large football stadium. Its nucleus would have the volume of a small marble in the center of the field. The electrons would be like tiny insects buzzing around in the stands. Encourage discussion among the students. Accept all reasonable responses.

6 Eureka #123 Electrons To give students a specific responsibility while viewing ASK, What are the three types of particles found in an atom? How are they alike and how are they different? Let s see if you were right. Students will validate their answers as they watch the video. FAST FORWARD and be ready to begin immediately following the opening segment. Audio is The story so far ---all substances in all three states of matter are made up of little round things called atoms. Visual is the same words written on screen. BEGIN video. PAUSE the video after each type of particle is highlighted. Use a dry erase marker to outline each type of particle on the television monitor as a further validation point. RESUME video after each point is validated. SAY, What is the name scientists give to the kernel of the atom? Use a dry erase marker to outline the word as a further validation point. SAY, How do atoms give the illusion of being solid spheres? Students will validate their answers as they view each segment of the video. STOP the tape as the narrator says, So what are you complaining about? Visually, a narrator is running into a lamppost. SAY, Rutherford calculated that the diameter of the atom is more than 100,000 times that of the nucleus. So an atom is mostly empty space! Invite students to draw each particle in an atom using the Bohr model of the atom. How can we draw electrons around the nucleus? Allow time for students to respond and to compare their anticipated responses. SAY, According to this model, electrons move in paths called energy levels. Think of the energy levels as rings around the nucleus. The energy levels, or rings are always referred to by numbers. Level I is the level closest to the nucleus. Each energy level of an atom can hold a certain number of electrons. SAY, The first energy level can hold up to 2 electrons. The second energy level can hold up to 8 electrons. The third energy level can hold up to 18 electrons, and the fourth can hold up to 32 electrons. The term shell is often used when referring to an energy level. Encourage students to study the diagram of the first four energy levels of an atom. Guide discussion as students brainstorm and respond.

7 Draw a diagram (or have a prepared transparency) of the first four energy levels of an atom showing the different numbers of electrons each holds. SAY, The electrons that have the most effect on the properties of an element are those found in the outer energy level. The outer energy level is the one farthest from the nucleus. SAY, All electrons are the same. They have the same mass and charge, but there is significance in the number of electrons and the way in which they are arranged in an atom. Atoms - Lab #1 Activity: Drawing Models of Atoms Materials (per student) Periodic Table Unlined paper Pencil Metric ruler Drawing compass (optional) SAY, This activity introduces a diagram as a model for the atom. This model is only a representation and is not three-dimensional. Before attempting this activity, review with the students how to determine the number of protons, neutrons, and electrons in an atom. Allow special needs students to work with a peer, if necessary. Procedure Use the Periodic Table, from the book, or from the Internet to find the number of protons, neutrons, and electrons in an atom in the first element of the Periodic Table. Calculate to determine number of neutrons in the atom. On a piece of unlined paper draw a circle 1 cm in diameter. This small circle stands for the nucleus. Write the number of protons in the circle next to a positive (+) sign. The P+ stands for protons. Write the number of neutrons in the circle next to the letter n. The N stands for neutrons. Show the correct number of electrons in each atom by placing them in the proper energy levels. Make the first energy level a dashed circle 3.0 cm in diameter. The circles around the nucleus show the energy levels. The e- stands for electrons. If needed make the second energy level a dashed circle 5.0 cm in diameter; make the third energy level a dashed circle 6.0 cm in diameter; make the fourth energy level a dashed circle 7.0 cm in diameter. On the correct circles write the number of electrons next to a negative (-) sign.

8 Using the steps above, repeat for the first 40 elements listed in the Periodic Table. This activity will take two class periods for optimum understanding. This activity can be extended to include more atoms until you feel students can draw a model of any given atom. Atoms - Lab #2 Activity: How is the Periodic Table Arranged? Materials (per student) Periodic Table Unlined paper Drawing compass (optional) Metric ruler Pencil Posterboard (per class) Scissors (per group of students) Tape (per group of students) SAY, The objective for this activity is to construct atomic model drawings and use them to make an example of a Periodic Table with only18 elements. Remember the current Periodic Table has 109 elements! Procedure A group of students will measure and cut out eighteen 8-cm squares of unlined paper (six students per group) On each square of paper, students will make a drawing to serve as a model of an atom for the first 18 elements listed in the Periodic Table. Have the transparency on the overhead projector to serve as a model for students to follow. The teacher also should draw some models of atoms for specific elements on whiteboard to get students started. For each model, use a circle 1.0 cm in diameter as a nucleus. Use the atomic number and the mass number to determine the number of protons and neutrons in the nucleus of each atom. Indicate these numbers on each drawing. Show the correct number of electrons in each atom by placing them in the proper energy levels. Make the first energy level a dashed circle 3.0 cm in diameter. Make the second energy level a dashed circle 5.0 cm in diameter. Make the third energy level a dashed circle 6.0 cm in diameter. Arrange the models in order of increasing atomic number on student desk or lab table. Look at the drawings and arrange them in a table so that each column contains atoms with similar features. Mount the squares in this arrangement on posterboard. Have students answer these questions using their Periodic Table. (Using these results to

9 draw conclusions will sharpen their critical thinking skills.) a) How many groups does your Periodic Table have? (should have 8 groups) b) How many periods does your Periodic Table have? (should have 3 periods) c) Where would you place an with an atomic number of 19 and a mass number of39? Explain the answer. (An atom with atomic number 19 would be placed below the atom with atomic number 11 in the fourth period because they both have one electron in their outermost energy levels.) Atoms Lab #3 Activity: What Are Some Properties of Metals and Nonmetals? Materials (per student) Samples of elements (Al, Cu, Fe, C, S, I, Sn, Pb, and Zn) Hydrochloric acid Small hammer Chisel or nail Conductivity apparatus Beaker 5 test tubes Dropper Goggles Apron Lab worksheet or Lab Journal Pencil SAY, This activity will give students an opportunity to explore some properties of metals and nonmetals. Ask students to group the materials in broad categories. Use many different samples of metals and nonmetals. Provide labeled samples of the elements listed. Providing chemical handbooks for students to use to determine physical properties would be advantageous. Students should observe each sample and describe the physical properties they would use to identify the elements. CAUTION: Remind students not to taste or touch the elements. Do not use any Group I metals because they are highly reactive. Since none of the material listed will react with HCL perhaps you could demonstrate the reaction with magnesium. Avoid hammering magnesium. Stress proper laboratory procedures in using iodine and hydrochloric acid. Procedure Wear goggles and an apron. Do not touch iodine crystals. Handle hydrochloric acid carefully. If spillage occurs, rinse area with plenty of water.

10 Obtain a small sample of each element. Observe the physical properties that are apparent. Record your observations for each sample in lab journal or worksheet. With the small hammer, try to drive the chisel or nail into the sample. This procedure tests the malleability of the sample. Record the observations. Using the conductivity apparatus, touch the two rods to the samples of Al, Cu, C, and Pb. Fill the bottom of a beaker with iodine crystals. Touch the electrodes to the crystals. Do the same for a beaker containing sulfur crystals. Record your observations. Place a sample of each element in different test tubes. Add a few drops of hydrochloric acid to each test tube. Record the observations. Post-Viewing Activities Atoms Lab #4/Extensions Students can use their observations of the physical properties of the elements to identify unknown samples of these elements. Three days after Atom Lab #3, provide the same samples without labels of their names. To distinguish the samples, number the samples. Students can try to identify the samples as metals or nonmetals and by name of the element. Lab #5 Research Assignment Assign a three page research paper on topics related to chemistry. Each student will be required to use traditional research sources and Internet searches. Math Component: Analysis of Date Lab #6 Atomic Math Purpose: Calculate the atomic number of mystery element X by doing the math. 1) Multiply the atomic number of Hydrogen by the number of electrons in Mercury, which has an atomic number of 80. Answer 2) Divide this number by the number of neutrons in Helium, atomic number 2, mass number 4. Answer 3) Add the number of protons in Potassium, atomic number 19. 4) Add the mass number of Carbon. Answer 5) Subtract the number of neutrons in Sulfur, atomic number 16, mass number 32. Answer 6) Divide by the number of electrons in Boron, atomic number 5, mass number 11. 7) Which of the following elements is the mystery element X?

11 A. fluorine; atomic number 9 B. neon; atomic number 10 C. sodium; atomic number 11 Answer (The final answer is sodium, atomic number 11) specific gravity for several substances. Calculate volume. Action Plan Organize a class trip to a nearby university chemistry department to observe chemistry students in labs. Share information with other students on the Internet. Students will prepare a list of common household chemicals. Students will research and report (via Internet) on the uses, chemical formulas, and chemical names of these substances. Extensions Language Arts/Reading Prepare written reports summarizing what has been learned about compounds, formulas, and ratios of these elements in compounds. Give oral presentations from the written reports to other classes. Encourage students to write essays on lab safety. Study the biographies of Marie Curie, Ernest Rutherford, Bohr, and Mendeleev. Mathematics Provide practice in atomic calculations. Compute density and

12 Art Make models of isotopes. Draw compounds showing molecular arrangement and movement. Social Studies Describe history of atomic models. Note the advantages and disadvantages of each form of the Periodic Table proposed in the twentieth century. Investigate the historical events that occurred during Mendeleev s lifetime ( ) when his systematic study of the properties of elements led to the Periodic Law. Resources Internet Alexander Arrangement of the Elements (3-D Model) Periodic Tables Table_of_the_Elements Periodic Table of Comic Books Periodic Table-Pictorial Visual Interpretation Sensational Slime Site sciedooutreach/funexperiments/quickndirty/ eric/slime.html Web Elements ITV Series Eureka #116 Molecules in Solids Eureka #117 Molecules in Liquids American Chemical Society Atomic Model del.htm Chemistry 4 Kids Chemistry Internet Resources Interactive Periodic Table

13 Name LAB #3 WORKSHEET ACTIVITY GOAL: WHAT ARE SOME PROPERTIES OF METALS AND NONMETALS? Data and Observations: Element Al Cu Fe C S I Sn Pb Zn Physical Properties Malleability Conductivity Acid Questions and Conclusions: 1. Based on testing, which of the samples were metals and which were nonmetals? Explain the answers. (Metals: Al, Cu, Fe / similar results; Nonmetals: C, S, I /similar results) 2. Why can metals be pounded without breaking? (because they are malleable: it may be too advanced to discuss metallic crystal structure at this middle school level) 3. What other common elements could be tested with these methods?(various answers)