Why is the following electron configuration not possible?
1-9-1

In numbering carbon atoms in the parent chain of a hydrocarbon, why would you number from right to left, rather than left to right

Which characteristics can be used to differentiate star systems? check all that apply.

Consider hydrogen in an excited state n = 5n=5 that emits photons to reach the ground state. there are various possible transitions other than straight to the ground state that can occur; for example, it can drop to the n = 3n=3 state followed by the n = 3n=3 to the ground state transition. which of the possible transitions will result in the emission of a photon in the visible region?