system
Given the following post, respond as if you're commenting on Reddit:
human
How do chemical reactions work on the quantum level?

I'm an undergrad student studying chemistry and biology where (especially in organic chemistry) we do a lot of "arrow pushing" (i.e. drawing arrows to signify where electrons travel during a chemical reaction). Earlier today I was watching a video in which Sean Carroll (physicist) goes on to explain how electrons actually form a "cloud" of probability around an atomic nucleus, where according to its wave function you can predict where you might find that electron if you went looking for it. He also stated, most importantly, that the electron is actually just a cloud of probability until you look for it, that the electron isn't anything more than a wave function until we look. What does that mean for my arrow pushing? If the electron is just a wave function does it collapse when chemical bonds are formed? What exactly goes on in this sense?
gpt
Arrow pushing is a way of visualizing the quantum processes. When you push two electrons from the valence shell of an atom to an "empty" orbital of another atom, these blend to make a new bond.

For example, you can take two electrons from an s orbital and put these into an empty s orbital of another atom. The spherical cloud of each s orbital then blends together to form an oblong sigma bond cloud of probability. The sigma bond is now just as the original s orbitals were a cloud that describes the probability of finding the two electrons in a given place.

Basically, the orbitals, which are clouds of probability, blend together when you push the arrows, so to speak, and create a newly shaped cloud of probability that spreads out between the two nuclei. 

This is nicely illustrated by two p orbitals interacting. For example, if you are forming an alkene, you already have a sigma bond between the C atoms. The p orbitals then can interact, through for example beta elimination, and form a pi bond. The p orbitals' clouds of probability have an hourglass shape, and the resulting pi bond (or double bond) looks like hotdog bun that wraps around the sigma (single) bond with no probability of finding the electrons on the C--C axis, just as the p orbital has no probability of an electron at the center of the hourglass.

So a chemical reaction creates a new wave function (sigma bond), a new cloud of probability. Collapsing the wave function refers to observing where exactly the electron is at any particular moment. This means that you no longer have a cloud of probability, but an actual measured location for that electron. In a sigma bond, that electron could be found near one atom, near the other atom, or in between the two.