According to the principles of classical chemistry, two atoms of the same element are considered identical. This assumption is based on the concept that all atoms of a particular element have the same number of protons, which defines the element itself. For example, all carbon atoms have six protons in their nuclei, and all hydrogen atoms have one proton.
In classical chemistry, atoms are considered indivisible and fundamental units of matter. At this level, there is no distinction made between individual atoms of the same element.
However, in the realm of quantum mechanics, which provides a more detailed description of atomic structure, the concept of identical atoms becomes more nuanced. According to quantum mechanics, atoms are not perfectly defined particles with fixed positions and velocities, but rather exist as probability distributions or wavefunctions. Quantum mechanics introduces the concept of quantum states and electron orbitals, which describe the probability of finding an electron in a particular region around the nucleus.
In quantum mechanics, identical atoms are treated as indistinguishable particles. This means that two atoms of the same element cannot be uniquely identified or distinguished from each other based solely on their properties. Quantum mechanics allows for the possibility of atom exchange, where two identical atoms can occupy the same quantum state or orbital.
Therefore, while classical chemistry treats two atoms of the same element as identical, quantum mechanics introduces the idea of indistinguishability and the possibility of atom exchange, which adds a deeper level of understanding to the nature of identical atoms.