model of the crystal structure of beta manganese, by C. E. Chapman, Chief Technician of the Crystallography Department, Cavendish Laboratory, English, 1952 / 1953
England; Cambridge; University of Cambridge; Cavendish Laboratory; Crystallography Laboratory; Austin Wing
Chapman, C. E.
chemistry; crystallography; demonstration
Jan. 1, 1952
Dec. 31, 1953
wood; metal; plastic
304mm width; 307 mm depth; 265mm height
Transferred via Mike Bown at the Department of Earth Sciences, University of Cambridge, Cambridge, from 27/07/2000. Made by Mr C. E. Chapman, Chief Technician at the Crystallography Department (Cavendish Laboratory), University of Cambridge, in 1952/1953.
on a plaque attached to wooden base
“beta - manganese”
model of the crystal structure of beta manganese. Made by Mr C.E. Chapman, Chief technician of the Crystallography department (Cavendish Laboratory) in 1952 / 1953.
Wooden base from which metallic vertical projections hold red and green spherical balls (manganese). The model shows the positions of the atom centres in a crystal of the metallic element manganese, in the beta- form. Red and green balls represent manganese atoms in sites which all have 12 nearest-neighbour atoms, but in two geometrically-different conformations.
James Hyslop; 'Crystal lattice models'; Explore Whipple Collections online article; Whipple Museum of the History of Science; University of Cambridge; 2008: https://www.whipplemuseum.cam.ac.uk/explore-whipple-collections/models/modelling-chemistry/types-molecular-models
In many metals all of the atoms are the same distance apart and surrounded by twelve other atoms (much like the arrangement of stacks of oranges in supermarkets). In manganese however, for reasons not fully understood, this is not the case. At room temperature some of the distances are shorter than others. This makes the arrangement of managese atoms in the crystal lattice more complicated than most other metals.
When metallic manganese is heated the crystal lattice undergoes changes in its structure before the metal melts. These different states are known as allotropes, and are named alpha, beta, gamma and delta to distinguish them. Between temperatures of about 700 to 1100 degrees centigrade, manganese exists in the beta state. As in the alpha state, not all the atoms are the same distance apart; but further, the atoms exist in two different geometrical arrangements (shown as red and green balls). This does not mean that they are a different kind of atom, just that their neighbouring atoms are arranged differently. This model of Beta-Manganese was made by Mr. C. E. Chapman, Chief technician of the Crystallography Department (Cavendish Laboratory) in 1952/53, and was acquired by the Museum from the Department of Earth Science at University of Cambridge.
Created by: Allison Ksiazkiewicz on 10/03/2014
Images (Click to view full size):