A chemical reaction [can/cannot] change an element into another element.

Depending on the context of your question: a chemical reaction can not! but Alpha decay is a kind of radioactive decay in which an alpha particle is emitted from an atom. An alpha particle consists of two protons and two neutrons. Therefore, when an atom of an element undergoes alpha decay, it loses two protons, which changes the atom from one element to another. This is because each different element is identified by the number of protons in its atomic nuclei.