system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How come material properties such as durability, color, electrical conductivity etc; look almost randomly chosen and change drastically when you change the number of protons and electrons in an atom?
gpt
If you take the number of milliseconds that have passed since some date, apply an entirely predictable mathematical function, then take the modulus or remainder, you end up with a number that seems random despite actually being completely predictable. 

Material properties work much the same way. 

Adding one electron or proton gives random seeming results, but if you add 8 protons and electrons to carbon, and enough neutrons to keep it stable, you get an element with much the same chemical and physical properties except for being heavier and having it's outer electrons less tightly bound due to their being further away. 

In absolute terms the colours only change slightly, but because we only see a tiny fraction of the electromagnetic spectrum that small absolute change can appear much larger and more random. 

As far as conductivity, both carbon and it's 8 units(+neutrons) heavier cousin can vary both their electric and thermal conductivity depending on how you put an allotrope of it together. The most extreme example being the carefully arranged crystal that you're using to read this.