google-chrome-stable is not available in the standard aptitude repositories, it requires some manual steps to install

1. Add a public key to the system (line 1)
2. Setup / register the new repository (line 2)
3. Update and install (line 3 and 4)

[shell]
wget -q -O – https://dl-ssl.google.com/linux/linux_signing_key.pub | sudo apt-key add –
sudo sh -c ‘echo “deb [arch=amd64] http://dl.google.com/linux/chrome/deb/ stable main” >> /etc/apt/sources.list.d/google-chrome.list’
sudo apt-get update
sudo apt-get install google-chrome-stable
[/shell]

Source: http://askubuntu.com/questions/510056/how-to-install-google-chrome