Questions about atoms: shells, attraction, elements

[Robert P]

My understanding is the atomic model has electrons occupying shells and in particular numbers, but what's known about why they arrange themselves into shells and in those particular numbers?

The teaching is that electrons have a negative charge and protons have a positive charge - but why do negative and positive attract? I.e. what are the mechanics of them being drawn toward each other?

If everything in the universe is made of the same constituent components, why do atoms arrange themselves into distinct elements?

 

[my2cts]

Q1: you could consult https://en.wikipedia.org/wiki/Atomic_orbital.

Q2: the "mechanics" is called electrodynamics. I do not know why electrons and protons attract, just how.
The why answer would require a deeper theory that the present one.
Take a look at https://en.wikipedia.org/wiki/Electric_charge

Q3: Just like with old school lego, many structures can exist based on only the two basic components, protons and neutrons.
Take a look at https://en.wikipedia.org/wiki/Chemical_element#Origin_of_the_elements to get an idea of how the various elements are thought to been formed.