Which of the following atoms will have the same electron configuration? I. N−3 II. O+2 III. F−1 IV. Li−1 V. Be+2?

The number of electrons of a neutral atom is equal to its atomic number.
An atom loses electron(s) to form a positive ion. An atom gains electron(s) to form a negative ion.

I. The atomic number of N is 7. The number of electrons of N⁻³ = 7 + 3 = 10
II. The atomic number of O is 8. The number of electrons of O⁺² = 8 - 2 = 6
III. The atomic number of F is 9. The number of electrons of F⁻¹ = 9 + 1 = 10
IV. The atomic number of Li is 3. The number of electrons of Li⁻¹ = 3 + 1 = 4
V. The atomic number of Be is 4. The number of electrons of Be⁺² = 4 - 2 = 2

The monatomic ions having the same number of electrons would have the same electron configuration.
N⁻³ and F⁻¹ have the same number of electrons, and thus they have the same electron configuration.

The answer: I and III