Why would you need 3 partitions? You only need one. Either sda2 or sda3 are big enough for a normal installation. 

The new installation normally will overwrite your boot sector, if you don't want that make sure to deselect that option. In that case you will have to boot
in the old 14.04 and run update-grub for it to find the new 14.04 and add it to the grub menu.

How to install Ubuntu 14.04 alongside the same existing OS in laptop?
Could anybody explain the following statement:

"The boundary surface is a common way to represent atomic orbitals, incorporating the volume in which there is about a 90 percent probability of finding the electron at any given time.

I don't understand what does the author means starting from "incorporating the volume.."
