| any element in any of the series of elements with atomic numbers 21–29, 39–47, 57–79, and 89–107, that in a given inner orbital has less than a full quota of electrons. |
| transition element n. Any of the metallic elements within Groups 3 to 12 in the Periodic Table that have an incomplete inner electron shell and that serve as transitional links between the most and the least electropositive in a series of elements. They are characterized by multiple valences, colored compounds, and the ability to form stable complex ions. Also called transition metal. |
transition element  (trān-zĭsh'ən) Pronunciation Key
Any of the metallic elements within Groups 3 through 12 in the Periodic Table. All the transition metals have two electrons in their outermost shell, and all but zinc, cadmium, and mercury have an incompletely filled inner shell (just inside the outermost shell). Transition elements form alloys easily, have high melting points, and have more than one valence because of their incomplete inner shells. See Periodic Table. See Note at metal. |