Subshell Electronic Configuration

To solve this problem, we need to understand the expression for the energy of an electron in a hydrogen-like ion. The energy level of an electron in such an ion is given by:

Where:

• is the atomic number of the ion.
• is the Rydberg constant (approximately ).
• is the principal quantum number of the electron's orbit.

By applying this formula, we know for He⁺ (where ) in the ground state ( ), the energy is given by:

The energy of an electron in the state for Be³⁺ ion (where ) is calculated as:

Simplifying, we find:

Comparing and the calculated , we see that for Be³⁺ in the state should still equal as per the original context for consistency.

Thus, both the He⁺ in and Be³⁺ in equate to .

Therefore, the correct choice is:-x