The WebUpd8 Atom PPA was updated so there are now Atom packages for both 32bit and 64bit available in the PPA.

To add the WebUpd8 Atom PPA and install Atom text editor in Ubuntu, Linux Mint and derivatives (now available for both 32bit and 64bit), use the following commands:

$ sudo add-apt-repository ppa:webupd8team/atom
$ sudo apt-get update
$ sudo apt-get install atom

The PPA is available for Ubuntu 14.10, 14.04, 13.10 and 12.04. Ubuntu 12.10 and 13.04 are no longer supported by Canonical!