${\mathrm{IP}}_1$ of molecular oxygen is identical with

Oxygen and Neon have similar values of the first ionization potential (IP₁) because they both have electronic configurations that are close to having a completely filled or completely empty outer electron shell.

Oxygen has an atomic number of 8, meaning it has 8 protons and 8 electrons. Its electronic configuration is 1s² 2s² 2p⁴. The first ionization of oxygen involves removing one electron from the 2p orbital, which requires 1313.9 kJ/mol of energy.

Neon, on the other hand, has an atomic number of 10 and has a completely filled outer shell. Its electronic configuration is 1s² 2s² 2p⁶. The first ionization of neon involves removing one electron from the 2p orbital, which requires 2080.7 kJ/mol of energy.

Although oxygen and neon have different numbers of electrons, their 2p orbitals have similar energies due to their similar electron configurations. Therefore, the energy required to remove an electron from the 2p orbital of oxygen is similar to the energy required to remove an electron from the 2p orbital of neon, resulting in similar values of IP₁.