My teacher recently taught us about Normal Elements ,Transition Elements And Inner Transition Elements.

He told us that If Outermost shell is incomplete then the element is normal element ,If both outermost and penultimate shell are incomplete in either elemental state or ionic state then they are Transition elements, And if Outermost, Penultimate and Pre-penultimate are incomplete in either elemental state or ionic state then they are Inner-Transition elements.

He also told us Zn ,Cd ,Hg are exceptions since they don't have any incomplete penultimate shell ionic or elemental state.

I have a question that in Zn$^{+2}$ have configuration 2,8,18 and it have all its shell complete.


1 Answer 1


If there were a «normal element», where are the «anormal» ones?

There are multiple approaches of «book keeping elements», e.g. IUPAC's dry way to count the columns in the periodic table of the elements by 1 up to and including 18. A more traditional one to consider them either as

which can be divided further into groups (e.g., alkali, alkaline earth elements) all while $(s, p, d, f)$ refer to the last electron formally added (aufbau principle) to the neutral atom.

But it is simplifying and the (man made) rule is known for exceptions in the d block (and even more so in the f block). It disregards that a shell A either fully, or exactly half filled and an empty shell B can over all yield a lower energy (hence a favored state) than two shells A and B both filled only partially. The experimental findings about the electronic configurations of the Zinc group (e.g. $[\mathrm{Ar}]\, 3d^{10}\, 4s^2$ for Zn) reflect this detail which requires an extra effort to memorize.


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