No, atheism and scientism are two different concepts, although they can intersect for some individuals.
Atheism is the disbelief or lack of belief in the existence of God or gods. It is a position on one specific question: the existence of a divine being. Atheism doesn't make any specific claims about how one should gain knowledge or what forms of knowledge are valid, which are questions of epistemology—the branch of philosophy concerned with knowledge, belief, and thought.
Scientism, on the other hand, is a philosophical position that regards science as the ultimate or sole source of knowledge and truth. People who subscribe to scientism believe that only scientific claims are meaningful, dismissing fields like philosophy, arts, and spirituality. This is a far broader stance than atheism and involves a particular view of what constitutes knowledge.
While some atheists may also subscribe to scientism, others do not. Some atheists might find value in philosophical or moral reasoning, or they may subscribe to non-religious spiritual beliefs. Similarly, not all those who believe in scientism are atheists. They may hold various religious beliefs that they see as consistent with their scientific worldview.
So, while there can be overlap, atheism and scientism are separate concepts. Atheism speaks to what one does or does not believe about the existence of deities, while scientism is a stance on what sorts of claims can yield knowledge.