An easily constructed model of a coordination polyhedron that represents the cubic closest packed structure

A hands-on experiment to obtain atomic and ionic radii with lumps of metal and ionic compounds is reported here. The experiment is performed with industrial-grade typical metals (iron, copper, aluminum, and lead) and single-crystal lumps of ionic compounds (sodium chloride, potassium chloride, and potassium bromide). Students measure the dimension of the given lumps with Vernier calipers and weigh them with a precision balance. After measuring the dimension and mass of the given lumps, students can calculate the atomic and ionic radius of each corresponding atom and ion with the obtained density values and information about the lattice structures. The obtained values of the metal atomic radii and the ionic radii of the ionic compounds are very close to the values in the literature. After this activity, the students came to appreciate that atomic radii, as typical submicroscopic and symbolic representations, are actually existing features and not an abstract concept. The experiment reported here is suitable for a first-year undergraduate general chemistry class as well as an introductory class at the high school level.

Section: Methodsmentioning

confidence: 99%

Section: Stacking Of Atoms and The Unit Cellmentioning

confidence: 99%

Hands-On Experiment To Verify Consistency from Bulk Density to Atomic and Ionic Radii with Lumps of Metals and Ionic Compounds

Kim

Seounghey

2019

“…It seems interesting for students to examine the packing efficiencies of various types of lattice structures experimentally and theoretically. The crystal lattice models in classroom demonstrations have been proposed. − Commercial display models are also available through companies such as Carolina Biological Supply Company and Indigo Instruments in the United States and Maruzen Company and Kenis Co. Ltd. in Japan . Although these models are very convenient to show the crystalline lattice in the classroom, it is difficult to understand the concepts of the unit cell, atomic arrangement, and coordination number of atoms using the space-filling-type models; on the other hand, the concepts of closest packing and packing efficiency in the lattice structures are hard to understand using the ball-and-stick type models.…”

mentioning

confidence: 99%

Using Latex Balls and Acrylic Resin Plates To Investigate the Stacking Arrangement and Packing Efficiency of Metal Crystals

Ohashi

2014

A high-school third-year or undergraduate first-semester general chemistry laboratory experiment introducing simple-cubic, face-centered cubic, body-centered cubic, and hexagonal closest packing unit cells is presented. Latex balls and acrylic resin plates are employed to make each atomic arrangement. The volume of the vacant space in each cell is measured by weighing water poured into the unit cell model, and the packing efficiency of each unit is obtained from the volume of vacant space. The observed values are compared with the theoretical calculations. Students can easily understand experimentally and theoretically that the packing efficiency of the face-centered cubic is the same as that of the hexagonal closest packing and significantly greater than that of the body-centered cubic. Moreover, they can understand the number of the neighboring atoms for any atom (coordination number) in each cell.

“…Various classroom demonstrations using crystal-lattice models have been described in this Journal and others presenting face-centered, body-centered, and simple cubic unit cells for first-semester general chemistry courses. Models presented include software programs, , BBs and watch glasses, paper and glue, − Styrofoam balls, , and others. − Commercial display models are also available through companies such as Carolina Biological Supply Company (Burlington, NC) and Indigo Instruments (Waterloo, ON, Canada). A very popular commercial crystal-lattice model set is the Solid-State Model Kit distributed through the Institute for Chemical Education.…”

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confidence: 99%

A Unit Cell Laboratory Experiment: Marbles, Magnets, and Stacking Arrangements

Collins

2011

An undergraduate first-semester general chemistry laboratory experiment introducing face-centered, body-centered, and simple cubic unit cells is presented. Emphasis is placed on the stacking arrangement of solid spheres used to produce a particular unit cell. Marbles and spherical magnets are employed to prepare each stacking arrangement. Packing efficiency is calculated using simple measurements of marble or magnet diameters and the dimensions of the stacking arrangement. Edge effects are introduced. Packing efficiency is subsequently calculated for various metal samples employing density measurements and literature atomic radii values. The stacking arrangement for each metal and its corresponding unit cell are determined by comparing packing efficiency values. Estimated percent unoccupied space values for water and air are also determined.