The element in question is oxygen, with an electron configuration of 2s² 2p⁶ 5s².
The given information indicates an element with 8 electrons in its n=4 energy shell and 2 electrons in its n=5 energy shell. To identify this element, we can analyze the electron configuration.
In the n=4 energy shell, there are 2 electrons in the s subshell and 6 electrons in the p subshell. Since there are 8 electrons in the n=4 shell, the electron configuration in the n=4 energy shell is 2s² 2p⁶.
For the n=5 energy shell, there are 2 electrons in the s subshell. Combining this with the electrons in the n=4 shell, the electron configuration in the n=5 energy shell is 5s².
Putting these together, the overall electron configuration is 2s² 2p⁶ 5s². This corresponds to the element oxygen (O) in its ground state. Oxygen has 8 electrons in its n=2 energy shell (2s² 2p⁴) and 2 electrons in its n=5 energy shell (5s²), which aligns with the provided information.
In summary, the element with 8 electrons in its n=4 energy shell and 2 electrons in its n=5 energy shell is oxygen, and its electron configuration is 2s² 2p⁶ 5s².