[e5volcano]

Hi, so far, in my AP Chem class we have just covered Atomic Structure [IE Ionization energy, electron orbitals]. We are basically reviewing and getting ready for a test but I am having some trouble. Here are some questions I have difficulty on:

1.  How do we know there is more than one shell of electrons in elements with a higher atomic number than 2?

2. How do we know there is more than subshell of electrons in elements of the second period of the periodic table and beyond?

3. How do we know that electrons are placed into pairs with opposite spin?

4. How did we come to understand electron structure?

[Mitch]

1. Because only 2 electrons can be placed in one shell.

[Astrokel]

I don't get 2, what is meant by "more than subshell of electrons"?

[Borek]

Most likely subshells are spdf, as opposed to shells KLMN.