1. In a diatomic molecule, molecular orbitals are formed by combining atomic orbitals of the two atoms.

2. For each atom, the orbitals considered are:

   • one $2s$ orbital
   • three $2p$ orbitals: $2p_x$, $2p_y$, $2p_z$

   So, per atom, total atomic orbitals = $1+3=4$

3. Since the molecule is diatomic, there are two atoms. Hence total atomic orbitals involved = $2\times 4=8$

4. The number of molecular orbitals formed is equal to the number of atomic orbitals combined.

   Therefore, total number of molecular orbitals formed = $8$

5. Final answer: $\boxed{8}$

Comparison with stored correct answer:

• Stored correct answer = $8$
• Derived answer = $8$
• Hence, they agree.