what’s the actual difference between different atoms besides just some protons, neutrons and electrions?

Question

What is it about, let’s say arsenic atoms, that makes it so much more deadly than gold for example. And please expand this to molecules too.

In: Chemistry

Answer 1

Everything about their properties truly emerges from the protons, neutrons, and electrons. That’s really just it. However, I can point out how that’s the case, which may illuminate things for you a little.

The amount of protons dictates the amount of electrons in a neutral atom. A hunk of plain carbon is going to have 6 protons and 6 electrons. So why is carbon black, solid at room temperature, why does it bond to itself in complicated chains, etc? Well, it has to do with largely with energy and electric fields. The protons create an electric field that the electrons interact with. This determines “where” the electrons can be around the atom and how much energy is binding them in their “spots”. The quotation marks are because electrons are quantum mechanical, so saying they’re in a particular place is kinda tricky.

So if you have a whole bunch of plain carbon in a clump, the protons and electrons determine the electric field around the atom, which affects how the individual atoms behave near each other. The electric attraction from these fields is relatively strong, which is why carbon is solid at room temperature. It sticks it all together into a chunk. Those fields are also why it’s black: the electric fields in the carbon resonate with light waves in such a way that they can absorb the energy from the light, making it opaque and black looking.

If we bond some other atoms onto our carbons to make something like propane, the electrons and protons are arranged in a new way. They have different electric fields, so they are attracted to each other and other molecules in a different way. Since they propane molecules are weakly attracted to each other, propane is a gas at room temperature. The molecules also hold a higher potential energy than plain carbon, which means we can set propane on fire to release that energy and get back carbon (and water and CO2).

So why is arsenic more dangerous than gold? Because the way it interacts with the molecules in your body (through the electric force mainly) is different than gold. It tends to bond to particular molecules in your body in a way that screws up how those molecules function, causing the machinery of your body to break down.