Answer:
Be²⁺: 1s²
Explanation:
The electron configuration is as follows:
Be: 1s²2s²
Be²⁺: 1s²
Be²⁺ ion has two electrons in the first shell. This is a stable electron configuration. The other stable electron configuration is an octet where there are eight valence electrons.
The electron configuration of Be²⁺ is the same as that of He (helium). Helium is a noble or inert gas.
Be²⁺ = He = 1s²