Yes, atoms remain after someone dies and are incorporated into the environment and other living beings:
Rearrangement
When someone dies, their atoms are rearranged into less ordered ways, which is called decay and entropy.
Incorporation
The atoms of a deceased person become part of the environment and are eventually incorporated into other living beings.
Diffusion
The atoms spread out and diffuse through the atmosphere, soil, and water.
Absorption
Light-utilizing organisms absorb the atoms and transform them into tissues, leaves, and tubules.
Incorporation into living beings
Oxygen creatures breathe in the atoms and incorporate them into their organs and bones. Pregnant women may also eat the atoms, and babies may contain them.
The law of conservation of matter states that matter cannot be created or destroyed, so all of a person's atoms must still be around after they die.
Proof enough of passing away for me.