Here's why:

* Democritus' Atomic Theory: Democritus, an ancient Greek philosopher, proposed that matter is made of tiny, indivisible particles called atoms. He believed these atoms were solid, homogeneous, and eternal. His ideas were primarily philosophical and lacked experimental evidence.

* Modern Atomic Theory: The modern atomic theory, developed by John Dalton in the 19th century, built upon Democritus' ideas, but it also included the following key points:

* Atoms can combine in whole number ratios to form compounds.

* Atoms of an element are identical in mass and properties.

* Atoms are rearranged in chemical reactions, but not created or destroyed.

Therefore, the idea of atoms retaining their identity during a chemical reaction is a concept from modern atomic theory, not Democritus' original ideas.