Which of the following are correct? Electrons generally occupy the lowest energy orbital first. The C atom has two unpaired electrons. The He atom has two electrons that have parallel spin in its 1s orbital. The arrangement of the orbitals is the same in a multielectron atom and a single-electron atom. In the Li atom, the 3s, 3p, and 3d orbitals have different energies. The He atom has one electron each in 1s and 2s orbitals.