Q: Given a scientific passage and an answer, generate a question for the given answer.
Passage: For the hydrogen atom, there is no problem since there is only one electron in the H atom. However, when we get to helium we see that the first three quantum numbers for the two electrons are the same: same energy level, same spherical shape. What differentiates the two helium electrons is their spin. One of the electrons has spin while the other electron has spin. So the two electrons in the 1s orbital are each unique and distinct from one another because their spins are different. This observation leads to the Pauli exclusion principle , which states that no two electrons in an atom can have the same set of four quantum numbers. The energy of the electron is specified by the principal, angular momentum, and magnetic quantum numbers. If those three numbers are identical for two electrons, the spin numbers must be different in order for the two electrons to be differentiated from one another. The two values of the spin quantum number allow each orbital to hold two electrons. The figure below shows how the electrons are indicated in a diagram. Answer: one
A:
How many electrons are in the hydrogen atom?