Atheism means without belief in a god. It is very important to note here the difference between 1. belief in no god, and 2. There is a small, yet important difference between the two.
Atheism is a lack of belief in god.
Atheism does not encompass any particular set of beliefs outside of the above definition, including and especially those of morality, cosmology, and teleology. Just because one atheist follows a certain set of morals does not mean that all atheists also share the same set of beliefs. There are as many different atheists out there as there are snowflakes. When kids grow up, they stop believing in Santa Claus, the Easter Bunny, and the tooth fairy. It is inherent in human nature to fear death and the idea of the world going on without our existence, so we make up god to console ourselves.