question_answer

The electronic configurations of Eu(Atomic No 63), Gd(Atomic No 64) and Tb (Atomic No. 65) are

A) \[[Xe]4{{f}^{7}}6{{s}^{2}},\text{  }\!\![\!\!\text{ }Xe\text{ }\!\!]\!\!\text{ }4{{f}^{8}}\text{ }6{{s}^{2}}\]and  \[[Xe]4{{f}^{8}}5{{d}^{1}}6{{s}^{2}}\]

B)  \[[Xe]4{{f}^{7}}5{{d}^{1}}6{{s}^{2}},\text{  }\!\![\!\!\text{ }Xe\text{ }\!\!]\!\!\text{ }4{{f}^{7}}\text{ }5{{d}^{1}}\text{ }6{{s}^{2}}\]and  \[[Xe]4{{f}^{9}}6{{s}^{2}}\]

C)   \[[Xe]4{{f}^{6}}5{{d}^{1}}6{{s}^{2}},\text{  }\!\![\!\!\text{ }Xe\text{ }\!\!]\!\!\text{ }4{{f}^{7}}5d16{{s}^{2}}\]and  \[[Xe]4{{f}^{8}}5{{d}^{1}}6{{s}^{2}}\]

D)   \[[Xe]4{{f}^{7}}6{{s}^{2}},\text{  }\!\![\!\!\text{ }Xe\text{ }\!\!]\!\!\text{ }4{{f}^{7}}5{{d}^{1}}6{{s}^{2}}\]and  \[[Xe]4{{f}^{9}}6{{s}^{2}}\]