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human
ELI5: Why is gold so soft, and why does it conduct electricity so well?
gpt
The entire group (column) on the periodic table of copper, silver, and gold are all really good conductors. Being in the same group means the outermost electrons of the elements have a similar configurations, there's just more inner electrons as the elements get heavier. As you can imagine, the outermost electrons are quite crucial for conducting electricity. They are also all quite soft metals, again because of outermost electrons which essentially give all the chemical and material properties other than density. Gold is just a lot more dense because the atoms are heavier. And while not silver, you'll note copper and gold share in common being about the only metals that are reddish and not grey. Copper is the second best conductor and by far cheapest, silver is the best conductor, and gold is the most corrosion resistant (so is used for electrical contacts sometimes when surface corrosion has a large impact on the conduction). 



So what makes this group special? 


Well, the electrons around atoms fall into various different orbitals, though don't take that too literally, they aren't balls circling around like the moon orbiting. These are patterns the electrons take around the atom, they are sort of smeared out in a region of space. They aren't circles, and lot aren't the spherical you might imagine. 


Completing filling certain levels of orbitals tend to make atoms more stable. Incomplete orbitals tends to make atoms more likely to simply give up or try and steal electrons to fill orbitals or empty out an incomplete one. This is the premise of pretty much the entirety of chemistry and material science, and it's by no means simple and none of our models are good enough to outright predict all properties from scratch for an atom. 


For a simple example, starting with hydrogen as really simple is has a 1s orbital. It's a small sphere around the atom. But this isn't filled, 2 electrons can fit in it. So hydrogen tends to try and share a second electron with another atom to fill it, like in water, H2O. The two hydrogens share a second electron with oxyegn. Helium has two electrons that fill this 1s orbital, so is very stable. Helium participates in virtually no chemical reaction and is always a gas as it won't stick to anything else, including itself. Hydrogen for examples share with itself to make H2 gas molecules. Helium atoms are content all on their own with their filled orbital. 


So that 1s filled, and 's' is the only or orbital shape in level 1. And you'll note, hydrogen and helium are the only two elements in the first row of the periodic table. That's why. Table came first based on material properties, but we later figured out that's why. Well, what's next? Well, levels 2. And the s shape shows up again, but so do others. 2s is again another sphere, but a larger one. You keep getting larger version of the same orbitals that we stick number in front of. You also get different orbital shapes, that can hold even more electrons than just 2 and have new letters like d and f. You'll note the periodic table gets more columns as you go down the rows. Some of these orbitals can hold a lot of electrons without going to a significantly higher energy level, that is the numbers. 


Anyways, back to group 11. That is, copper, silver, gold. So, the d orbital that metals in rows just before this group had been trying to fill is now filled. These electrons are happy and stable. This means they don't help with bonding (at least within the elements in their pure form) or help with electrical conduction. This leaves just a lone electron in the #s orbital, no where near filling the orbital up but pretty easy to give away. Copper it is 4s. Silver 5s. Gold 6s. For all of them, this lone electron is very weakly attached. It forms very weak bonds the atoms and has little attachment to the atoms.



Firstly, this gives these metals a sea of easy to move electrons floating around them, although a lot of metals have this to some degree. The sea also isn't too full, so lots of space for these electrons to move. Secondly, this means the bonds are really weak. There's where the softness and ductility comes from, weak bonds that are happy to break and reform to a new atom in a very fluid way. 


And as for conduction, two things matter. How many charge carriers, that is free electrons, you have. And how far they can move freely before they smash into something. 


What do electrons conducting electricity smack into? Well, firstly impurities. Impure gold and copper don't conduct as well. But those aside, the atoms themsleves, but only if they are vibrating. The electrons move easily around the stationary crystal, but when you add vibration, that is heat or temperature, the electrons will start to have collisions and hence have resistance. But gold, copper, and silver have weak bonds. Which means weak vibration, which means low impedance to the movement of electrons. You'll note aluminum, the other common conductor rivaling copper, is also soft.  Though not for the same d-orbital just filled and lone electron in the s-orbital reason, but a different but similar setup. Aluminum isn't as good as conductor as copper, but it's cheaper and more importantly is really light, actually making it a better conductor by weight (but not by size).