Question

Which of the following is not a transition element?
A. $Mn$
B. $Fe$
C. $Cu$
D. $K$

Answer 1

Transition element or we can say transition metals are the elements which have d- orbitals that have partially or fully filled electrons in it. In order to answer the above question, we need to look at the electronic configuration of all elements. The elements which do not have the d-orbitals in it, cannot be regarded as transition elements.

Complete answer:
Transition elements are the elements which are having a d- subshell which has partially or fully filled electrons. Basically, we can say that transition elements belong to the d-block element. These elements are presented in the middle of the periodic table.
Let’s look at the electronic configuration of each element given in the question.
A. $Mn$
The given symbol “$Mn$” indicates that it is Manganese. It’s atomic number is $25$.
The electronic configuration of manganese is $[Ar]3{d^5}4{s^2}$. It contains d- orbitals so it is a d- block element. Hence, it is a transition element.
B. $Fe$
This symbol “$Fe$” represents Iron. The atomic number of iron is $26$.
The electronic configuration of iron is $[Ar]3{d^6}4{s^2}$. It contains d- orbitals so it is a d-block element. Hence, it is a transition element.
C. $Cu$
This symbol “$Cu$” represents copper. The atomic number of copper is $29$.
The electronic configuration of iron is$[Ar]3{d^{10}}4{s^1}$. It also contains d- orbitals so it is a d-block element. Hence, it is a transition element.
D. $K$
In this case, the given symbol “$K$” represents potassium. The atomic number of Potassium is $19$.
The electronic configuration of potassium is $[Ar]4{s^1}$. This element does not contain d- orbital so it is not a d-block element. Hence it is not a transition element.
Therefore, the correct answer is option (D) i.e. Potassium.

Note:
It should be noted that transition elements have a lesser number of electrons in the outermost shell so they all act as metals. They show all the characteristics of metals like malleability, ductility. Also, they are good conductors of heat and electricity.