Answer:
Here's what I get.
Explanation:
Ba is element 56. Its electron configuration is
1s² 2s²2p⁶ 3s²3p⁶ 4s²3d¹⁰4p⁶ 5s²4d¹⁰5p⁶ 6s²
That's a lot of writing.
To lessen the work, chemists have developed the noble gas notation.
The core electrons of Ba (listed in boldface) have the same electron configuration as Xe, the noble gas found two atoms earlier in the Periodic Table.
Chemists replace the core electron configuration with the symbol of the corresponding noble gas.
The noble gas notation for Ba becomes
Ba: [Xe]6s².
