Hi, I just have a few questions I'm struggling to find straightforward answers to online. The 4 quantum numbers of an electron in an atom describe the energy level, shape and suborbital of the orbital, and the fourth assigns a value to the electron's spin. Question 1) why is it in lone atoms that having two electrons of opposite spin is more energetically desirable? Why is there this "push" towards having all suborbitals filled with 2 electrons with opposite spins? 2) why do covalent bonds, for example sigma bonds, form due to two electrons also having opposite spins? What's so great about having a bond with two electrons in it of opposite spin compared with having two separate atoms each with a lone electron of either spin? Question 3) I understand that some covalent bonds take in energy while most release energy, but I don't really understand why. Does the uniting of two electrons from two orbitals into one orbital... just... release latent energy due to opposite spins sharing one orbital? 4) Does anyone know why orbitals change shape when formed? For example, an sp3 orbital joins an s orbital, to form a sigma orbital. I know orbitals are wavefunctions, so why does the wavefunction change form when two orbitals become one? Does it go back to the quantum numbers?