According to the law of conservation of mass, atoms cannot be created or destroyed in a chemical reaction. However, atoms can undergo nuclear reactions where they can be transformed into different elements or isotopes.
As for the total number of atoms in the universe, it's difficult to determine with certainty. The universe is vast and contains an enormous number of atoms. Stars, galaxies, planets, and other celestial bodies are composed of atoms, and there are also atoms present in interstellar and intergalactic space.
While we cannot definitively say if the number of atoms in the universe is finite or infinite, based on current scientific understanding, it is generally believed that the number of atoms is incredibly large but finite.