http://www.ck12.org Chapter 6. The Periodic Table
Transition Elements
Transition elementsare the elements that are found in Groups 3-12 on the periodic table. Thedsublevel, which
is in the process of being filled, is in a lower principal energy level than thessublevel filled before it. For example,
the electron configuration of scandium, the first transition element, is [Ar]3d^14 s^2. Remember that the configuration
is not written in the same order as the sublevels are filled; the 4ssublevel gets filled before electrons are placed into
3 dorbitals. Because they are all metals, the transition elements are often called the transition metals (Figure6.13).
As a group, they display typical metallic properties but are less reactive than the metals in Groups 1 and 2. Some of
the more familiar transition metals are unreactive enough to be found in nature as pure elements, such as platinum,
gold, and silver.
FIGURE 6.13
Silver (left) and chromium (right) are two
typical transition metals.Many transition elements make compounds that are distinctive for being vividly colored. Electron transitions that
occur within thedsublevel absorb some of the wavelengths present in white light, and the wavelengths that are not
absorbed are perceived by observers as the color of the compound (Figure6.14).
FIGURE 6.14
Transition metal compounds dissolved in
water exhibit a wide variety of bright col-
ors. From left to right are shown solutions
of cobalt(II) nitrate, potassium dichro-
mate, potassium chromate, nickel(II) chlo-
ride, copper(II) sulfate, and potassium
permanganate.The
The transition elements found in Groups 3-12 are also referred to as thed-block, since thedsublevel is in the process
of being filled. Since there are fivedorbitals, each of which can accommodate two electrons, there are ten elements
in each period of thed-block. The general electron configuration for elements in thed-block is (n- 1)d^1 −^10 ns^2. The
dsublevel being filled belongs to a principal energy level that is one lower than thessublevel that has just been filled.
For example, the configuration of zirconium (Zr) is [Kr]4d^25 s^2. The group number can easily be determined from