What is the electronic configuration of the element with atomic number 57?

What is the electronic configuration of the element with atomic number 57?

Correct Answer: [Xe] 6s2

Step 1: Identify the element with atomic number 57. This element is Lanthanum (La).
Step 2: Determine the nearest noble gas before Lanthanum. The nearest noble gas is Xenon (Xe), which has an atomic number of 54.
Step 3: Write the electron configuration for Xenon, which is [Xe].
Step 4: Count the remaining electrons after Xenon. Lanthanum has a total of 57 electrons, so we need to account for 3 more electrons (57 - 54 = 3).
Step 5: The next energy level after Xenon is the 6th shell. The first two electrons go into the 6s subshell.
Step 6: After placing 2 electrons in the 6s subshell, we have 1 electron left to place. However, for Lanthanum, we only need to write the configuration as [Xe] 6s2, since the 6s subshell is filled with 2 electrons.

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