How many electrons does it take to fill the MOs formed from the combination of the 2p orbitals of two atoms?

To determine how many electrons it takes to fill the molecular orbitals (MOs) formed from the combination of the 2p orbitals of two atoms, we need to analyze the situation in terms of molecular orbital theory:

1. Molecular Orbital Formation: When two atoms come together, their atomic orbitals combine to form molecular orbitals. In the case of the 2p orbitals, two types of MOs are formed: bonding and antibonding orbitals.

2. Counting Atomic Orbitals: Each atom contributes three 2p orbitals (2p_x, 2p_y, 2p_z). When two atoms combine, the total number of atomic orbitals combined is $3 + 3 = 6$.

3. Formation of Molecular Orbitals: These six 2p atomic orbitals will combine to form six MOs: three bonding MOs and three antibonding MOs. The general configuration is as follows:

   • $\sigma_{p}$ (bonding)
   • $\pi_{p}$ (bonding)
   • $\pi_{p}^*$ (antibonding)
   • $\sigma_{p}^*$ (antibonding)

4. Filling the MOs with Electrons: According to the Pauli exclusion principle and Hund's rule, each MO can hold two electrons with opposite spins.

5. Total Electron Capacity: Since there are three bonding MOs and three antibonding MOs, the total number of electrons that can fill the bonding MOs is 6 (2 electrons in each of the three bonding MOs).

Final Answer

It takes 6 electrons to fill the molecular orbitals formed from the combination of the 2p orbitals of two atoms.