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~ ,,> There are 92 naturally occurring kinds of atoms found on Earth, each with a different number of protons, electrons, and neutrons. The number of Key Question electrons in the outermost shell determines the chemi How can we make a model of .,n atom that shows its cal properties of the atom. Each different kind of atom is called an element and is identified by its atomic electrons, protons, and neutrons? number (the number of protons in the atom). Chem Learning Goal ists also define an element as a simple substance that Students will make simple models of atom. cannot be broken down into any smaller component by ordinary chemical reactions. Protons and electrons have a property called Guiding Document Project 2061 Benchmarks charge. All electric phenomena are caused by charges. .. All mailer is made up of atoms, which are far too By convention, protons are said to have a positive small to see directly through a microscope. The charge, and electrons a negative charge. Neutrons have no charge. Most atoms have the same number atoms of any element are alike but are different from atoms ofother elements. of protons and neutrons and are electrically balanced. If an atom has different numbers of protons and elec • Models are often used to think about processes [hat happen 100 slowly, too quickly, or on too trons, it is called an ion. If there are more electrons smail a scale to obserue direclly, or thaf are too than protons, it is a negative ion. If there are more uastto be changed deliberately, or that are poten protons than electrons, it is a positive ion. tially dangerous. It is impossible to picture atoms accurately; for example, electrons have a dual nature and can take Science the form of both particles and waves. The only accu rate model of an atom is an abstract, mathematical Physical science one. Since this type of model does not help most matter atoms people understand atoms, several other models are usually used when describing atoms. The most Integrated Processes common is the Bohr model. It pictures a central mass Observing (nucleus) made up of protons and neutrons orbited by electrons. Comparing and contrasting The Bohr model, like all non-mathematical ones, Materials has distortions of the size and space relationships within an atom. It is difficult to accurately convey the Per set of atoms: vastness of the empty space within atoms. If an atom construction paper plastic bag of miniature marshmallows, 10 of each were two miles in diameter; it would appear to be solid. three different colors since the electrons would be orbiting the outer shell at 'almost the speed of light. Yet, its nucleus would glue only be about the size of a golf ball and its electrons markers the size of BBs; all the rest would be empty space.' Background Information The atom model used in this lesson is similar to All matter is made up of atoms, which in turn are the Bohr modeL While not very accurate. it does show the basic parts of an atom and the atomic shells. It is made up of smaller particles called protons, neutrons, and electrons. Together, protons and neutrons form intended to be a starting point for students in building the central core, or nucleus, of an atom. Electrons, their conceptualization of the atom. which have only 1/1840 the mass of protons and Management neutrons, orbit the nude.us in layers called shells. l. Students can work alone or in groups. There are rules by ~hich the shells operate.ln,the 2. Plastic bags with the marshmallows should be innermost shell near the nucleus, only two electrons, made up ahead of time for individual groups. can orbit. In the second shell. only eight can orbit. 3. Three colors of colored dots, colored cereal, or Other shells beyond this can hold more electrons, except for the outermost shell. which never has more construction paper circles can be used instead of than eight. marshmallows to represent the protons, etectrons, and neutrons. Topic Atomic structure (, \' " , :i: " ,i I I I ELECTRICAL CONNECTIONS 1 © 2005 AIMS Education Foundation , ,,, ,, 7. 4. Since electrons are SO much smaller than protons and neutrons, smtsller bits of m;"rsrunallow, or smaller colored dots can be used to represent them. 5. The activity sheet can be used to make models of atoms if the other materials are not available. Procedure 1. Students will make models of three different atoms. Drawa diagram of an atom on the board and tell the students that atoms are made up of three impor tant parts: the protons, neutrons, tsndthe electrons. You may want to tell students about the charges on protons (+) and electrons (-). 2. Explain that atoms are the building blocks of matter and that they differ only in the number of protons, electrons, and neutrons. Tell students that the number of protons present (the atomic number) determine what type of atom it will be. For example, carbon has an atomic number of six. It has six protons, six electrons, and usually six neutrons. 3. Demonstrate how to make a model of an atom. Using three different colors of marshmallows and a piece of construction paper. construct a model or a helium alom. Glue two "protons" (first color of marshmallow) lind two ~neutrons" (second color) together in the center of the "atom" to form the nudeus. Draw a cirde (shell) around this nucleus imd glue two "electrons~ (third color) somewhere on the circle. Since the mass of the electrons is much less than the mass of the protons and neutrons, use small pieces of marshmallow to represent each electron. DISCUSS the fact that these marshmallow models are only like real atoms in a few ways (they show the'three main particles in atoms, they show the nucleus made of protons and electrons, they show the electrons as orbiting the nucleus in shells, they show that electrons and protons have charge). Explain thl:it models sometimes help us. under stand difficult concepts. Emphasize the fact that real atoms are incredibly small and wondrous things with many amazing properties. Connecting Learning I. How are all atoms the same? [They are made of electrons, protons, and neutrons.J 2. What is at the center of every atom? [The nucleus, which is made of protons and neUlTons.) 3. What orbits the nucleus? [electronsJ 4. How is the nucleus of the hydrogen atom dIffer ent from the nucleus of the helium atom? [The hydrogen dtom does not have any neutrons in its nucleus.J 5. How is the carbon atom different from the helium atom? [It has electrons orbiting in two electron shells J 6. What atomic particle is related to the \',ord elec tricity? {electron} 7. How could we build models of other aloms? [Use different numbers of marshmallows. J 8. What are you wondering now? Extensions 1. Use the actiVity sheet to make a model of an oxygen alom (atomic number is eight). 2. Make models of other atoms. You will need more than two shells for larger atoms. 3. Use other materials to make models of atoms. 4. Study the periodic tabie. Look at how the number of electrons in the outer shell of an atom deter mines what family it is in. "I ~ ~ "I"" \:~ H f I , j, I I 1 ! ,I 4. Distribute the marshmallows and construction paper. Have students construct a hydrogen atom (one proton, one electron), a helium ctom (two protons, two neutrons, two electrons), and a carbon atom (sIx protons, six neutrons, six elec trons). The first shell (inner circle) of the carbon atom has two electrons, the second shell (outer circle) will have four electrons. 5. Students may use markers to drctw the electron shells. Markers can also be used to put a (+) on each proton and a (-) on each electron. 6. Students will use the remaining three marshmal lows to make a key for their atom model (there will be one extra "neutron" left over). For example, pink ;. proton (+); green'" neutron: yellow", electron (-). " ELECTRICAL CONNECTIONS 2 ', n hellum atom ,!, II © 2005 AIMS Education Foundation 1 I ~, , . ~ '-I • .-....1 Key Question f) How can we make a model 1~~§§-~~~=J of an atom that shows its ~~'" : electrons, protons, and ~eutrons? _.-J ,I 1, " , i': !' . i j ~ i', j"" ,-.,., ~.~, Learning Goal , : , I " make simple models of atoms. ," I' I -! , ,, ", " ~. " :, I (. ELECTRICAL CONNECTIONS 3 © 2005 AIMS Education Foundation ,J ,. I . • GGGG GGGG ELECTRICAL CONNECTIONS 0000 0000 4 8 8 8 8 8 8 8 8 © 2005 AIMS Educ.Uon Found.tion • II i , Connecting Learning 1. How are all atoms the same? 2. What is a the center of every atom? 3. What orbits the nucleus? 4. How is the nucleus of the hydrogen atom different from the nucleus of the helium atom? 5. How is the carbon atom different from the helium atom? 6. What atomic particle is related to the word electricity? .i. i;' \ 7. How could we build models of other atom? :~. 8. What are you wondering now? • '>";. ,. ~~'; ....'., ~:l 'ELECTRICAL CONNECTIONS 5 © 2005 AIMS Education Foundatlon