The maximum number of electrons that can be found in the 3s subshell is 2.
This is based on the principles of quantum mechanics and electron configuration in atomic structure. Each orbital can hold a maximum of two electrons, which must have opposite spins according to the Pauli exclusion principle. In the case of the 3s subshell, there is only one s orbital, and therefore it can accommodate a maximum of 2 electrons. This is true for all s subshells, regardless of their energy level. Therefore, in the 3s subshell, the maximum is also 2 electrons.