Explanation
Step 1: Energy formula for hydrogen-like species
En = −13.6 × Z² / n² (in eV)
Step 2: Values for Be³⁺
Atomic number Z = 4
First excited state ⇒ n = 2
Step 3: Substitute values
E = −13.6 × (4)² / (2)²
E = −13.6 × 16 / 4
E = −13.6 × 4 = −54.4 eV
Step 4: Take magnitude and nearest integer
|E| ≈ 54 eV
Correct Answer = 54