Question

Europium is a:
A. s-block element
B. p-block element
C. d-block element
D. f-block element

Answer 1

Hint: The block of the element can be identified based on the outermost orbitals. The valence electrons of the europium enter into the f-orbital. On the basis of the number of valence electrons we can find which group it belongs to.

Complete answer:
In the periodic table four orbitals are there. These are: s, p, d and f in which the electron enters. All these orbitals contain electrons in an element but the orbitals that receive the last electrons are known as valence orbitals and the valence orbital indicates the block type of which the elements belong.
The atomic number of the europium is 63.
The electronic configuration of the europium element is as follows:
$\left[ {{\text{Xe}}} \right]\,{\text{4}}{{\text{f}}^{\text{7}}}\,{\text{6}}{{\text{s}}^{\text{2}}}$
The s-orbitals are completely filled and the f-orbital has seven electrons. The energy of 6s orbitals is less than the 4f orbital, so, the electron first enters into 6s orbitals, and then the remaining valence electrons enter into 4f orbital.
The valence electrons of the europium element enter into f-orbital therefore, the europium is an f-block element.

So the correct option is (D).

Additional Information: The period of the element tells the principal quantum number of the valence shell of the element. The group number tells the number of valence electrons entered in the outermost orbital. F-block elements from atomic numbers 58 - 71 are known as lanthanides and elements from atomic numbers 90 - 103 are known as actinides. So, europium is a lanthanide.

Note: The block of the element tells the type of outermost orbital which receives the last electrons. The atomic number of xenon is 54 so, if an atom contains electrons more than a noble gas its electronic configuration is shown by the symbol of noble gas and valence electronic configuration.