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) has an atomic number of 57. To find the electron configuration, we start with the electron configuration of Xenon \([Xe]\), which corresponds to the atomic number 5(4) Now, we fill the remaining electrons for the next elements.
For lanthanum, after \([Xe]\), the configuration is: \[ [Xe] \, 4f^1 \, 5d^1 \, 6s^2 \] This means lanthanum has one electron in the 4f orbital, one electron in the 5d orbital, and two electrons in the 6s orbital.
Thus, the correct answer is: \([Xe] 4f^1 5d^1 6s^2\).
Final Answer: \[ \boxed{\text{The correct configuration is (4), } [Xe] 4f^1 5d^1 6s^(2)} \]