Xe is xenon, which is an element. The string you ask about is not an element.
Ce
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Europium
No element has this as the ground state. Gadolinium has the right number of electrons but its ground state is [Xe] 4f7 5d1 6s2. The second number in each group should be a superscript.
Element Os
It's not barium. [Xe] 6s2 is barium. But [Xe] 6s2 4f14 5d10 (or 4f14 5d10 6s2 - it doesn't matter which way round) is Hg (mercury).
The electron configuration of Pb is [Xe]4f145d106s26p2
The noble gas notation for samarium is [Xe] 6s2 4f6.
[Xe] 4f7 6s2
No element has this as the ground state. Gadolinium has the right number of electrons but its ground state is [Xe] 4f7 5d1 6s2. The second number in each group should be a superscript.
[Rn] 5f14 7s2
Europium is a chemical element with symbol Eu and atomic number 63 and a member of the lanthanides (f-block, [Xe] 4f7 6s2, in period 6). It is a ductile metal.
Europium
Barium: [Xe]6s2
Element Os
Osmium (Os, #76).
that would not be an element itself, but a compound containing a few different elements: xenon, sulfur, and one undiscovered element ("F" does not currently exist)
the element is tungsten with the electronic configuration Xe 4f14 5d4 6s2
This electron configuration is for osmium (Os).
Long-hand version: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 5s^2 4d^10 5p^6 6s^2 4f^7 Short-hand version: [Xe] 6s^2 4f^7 Note: The "^" symbol means the the following number is in the form of a superscript.