Biomedical Engineering Reference
In-Depth Information
In view of Moseley's findings, the positions of cobalt and nickel had to be re-
versed in the periodic system. Although Co has the larger atomic weight, 58.93
compared with 58.70, its atomic number is 27, while that of Ni is 28. Moseley also
predicted the existence of a new element with
Z
= 43
. Technetium, which has no
stable form, was discovered after nuclear fission.
2.11
Auger Electrons
An atom in which an L electron makes a transition to fill a vacancy in the K shell
does not always emit a photon, particularly if it is an element of low
Z
. A different,
nonoptical transition can occur in which an L electron is ejected from the atom,
thereby leaving two vacancies in the L shell. The electron thus ejected from the
atom is called an Auger electron.
The emission of an Auger electron is illustrated in Fig. 2.11. The downward ar-
row indicates the transition of an electron from the L
I
level into the K-shell vacancy,
Fig. 2.11
Schematic representation of an atomic transition that
results in Auger-electron emission.
