Question

The atomic number of Lanthanum is 57. Its electronic configuration will be ......

• A. \([Xe] 5d^1 6s^2\)
• B. \([Xe] 4f^1 5d^1\)
• C. \([Xe] 4f^3\)
• D. \([Xe] 4f^1 5d^1 6s^2\)

Hint:

For Lanthanides, the electron configuration often involves filling the 4f orbital after the 6s orbital.

Answer 1

The Correct Option is D

Lanthanum (La), with atomic number 57, has an electron configuration derived from Xenon ([Xe]). The electron configuration for lanthanum is: \[[Xe] \, 4f^1 \, 5d^1 \, 6s^2\]This indicates one electron in the 4f orbital, one electron in the 5d orbital, and two electrons in the 6s orbital. Therefore, the electron configuration is \([Xe] 4f^1 5d^1 6s^2\). Final Answer: \[\boxed{\text{The correct configuration is } [Xe] 4f^1 5d^1 6s^2}\]