Question

The lanthanide element that has the electronic configuration $ \left[ Xe \right]4{{f}^{7}}5{{d}^{1}}6{{s}^{2}} $ is:
(A) Lutetium.
(B) Terbium.
(C) Ytterbium.
(D) Gadolinium.

Answer 1

Hint: We know that the elements which are known by the terms mentioned in the options. We have to identify the element from the given electronic configuration Look at the electronic configuration and find out in which orbital the valence electrons are present. Find out how many electrons are present in the valence shell to get the answer.

Complete answer:
We can see that the 5d orbital is incomplete; this indicates that the given element belongs to d-block and not sblock. So, this element is not an alkaline earth metal.
- It has the valence shell $ 6s $ which means the element belongs to the sixth period. We know that lanthanides are present in the sixth period
An alkaline earth element: Alkaline earth elements are Beryllium, Magnesium, Calcium, Strontium, Barium and Radium. The second group of s-block in the periodic table consists of alkaline earth metals. They have the valence shell electronic configuration $ n{{s}^{2}} $ where n is the valence shell.
A transition element: Transition elements are the elements present in the d-block of the periodic table. Some transition elements are Titanium, Chromium, Copper, Nickel, Manganese, etc. They have the valence shell electronic configuration $ (n-1){{d}^{1-10}}n{{s}^{2}} $ where n is the valence shell and (n-1) is the penultimate shell.
An inert gas: Inert gases are noble gas elements like Helium, Argon, Neon, Krypton, Xenon and Radon. They belong to the last group in the periodic table. They have the valence shell electronic configuration where n is the valence shell.
A rare earth: Rare earth elements are a group of $ 17 $ elements which are present in very low concentration levels on ground. Rare earth elements include all the lanthanides and Scandium and Yttrium.
Gadolinium is a chemical element with the symbol Gd and atomic number $ 64. $ $ \left[ Xe \right]4{{f}^{7}}5{{d}^{1}}6{{s}^{2}} $ is the electronic configuration of gadolinium. $ $

Note:
Remember the names of some characteristic groups in the periodic table like alkali metals, transition metals, chalcogens, halogens, inert gases or noble gases, lanthanides, actinides and rare earth elements. For such questions, try breaking down the given electronic configuration and try the method of elimination to get the correct answer.