Question

An element with the electronic configuration $\left[ {Xe} \right]4{f^{14}}5{d^7}6{s^2}$ is:
A.An alkaline earth metal
B.A transition metal
C.An inert gas
D.A rare earth

Answer 1

To answer this question, you must recall the terms used for various types of elements in the periodic table, their positions and the general electronic configuration. The number of electrons in the valence shell of an atom determines its properties to a large extent.

Complete step by step answer:
- We are given the electronic configuration of the element in the question as $\left[ {Xe}\right]4{f^{14}}5{d^7}6{s^2}$.
- We can clearly note that the d orbital is not completely filled. Hence, the given element belongs to the d- block of the periodic table and is not an alkaline earth metal or an inert gas.
- The valence shell of the given element is 6s. This implies that the element belongs to the sixth period of the periodic table where the lanthanides are also present. But, the 4f orbital is completely filled and so is not a rare earth element as well.
- We can conclude that the given element is a transition metal.

Thus, the correct answer is B.

Note:
- Alkaline earth metal: These are the metals present in the group two of the s- block of the modern periodic table. The elements of this group are Beryllium, Magnesium, Calcium, Strontium, Barium and Radium. The valence shell electronic configuration of the alkaline earth metals is given as $n{s^2}$.
- Transition metal: The elements present in the d- block of the periodic table, i.e., they correspond to the filling of the penultimate d orbital. The valence shell electronic configuration for these metals is given as $\left( {n - 1} \right){d^{1 - 10}}n{s^2}$.
- Inert gas: They are noble gases and are members of the last group of the periodic table. The valence shell electronic configuration for these elements is given as $n{s^2}n{p^6}$.
- Rare earth: These are elements present in very low amounts in the earth’s surface. They consist of 17 elements which are 15 lanthanides, scandium and yttrium.