For the record, so that we are all speaking the same language, the term �atheism� in the most basic sense means �without / belief in a god�, be it one or many, none. An atheist is simply, one who does not believe in any god, end of story . . . ?
. . . Hardly! . . .
Atheism is the default position with which we are all born. Unless you come out of the womb (or an egg) declaring, "I am the son (or daughter) of God", until one has gained the capacity to believe in Santa Claus or the like they are without belief . . . in anything, real or imaginary whether they or it be born or unborn, dead or alive. Likewise dogs, trees and rocks are implicitly atheists as they too do not believe in a god.
When one asserts that no god can, does or has ever existed, then they have become a specific breed of atheist, an explicit atheist.
Agnostics also come in a variety of forms. Even an agnostic can be an atheist, as many are by virtue of not holding a belief in the existence of a god/s, although some choose to be theists (one who believes in a god or gods), in spite of (by definition) their primary belief that god's existence can not be known.