Which of the following transitions in the sodium atom is allowed ?

Question

Which of the following transitions in the sodium atom is both allowed and might lead to emission of light from a sodium lamp? Choose one of the following answers and justify your answer.

a) 5s → 3s

b) 3s → 6d

c) 3p → 3s

d) 6f → 4p

e) 4s → 5p

Answer 1

for emission of a photon to occur, the transition must be from an upper energy level to a lower energy level; the emitted photon will have an energy equal to the energy difference of the two levels involved

this criterion rules out b) and e)

also, the transition rules for sodium include delta l = +/- 1; in other words, allowed transitions can occur only when the l quantum number changes by plus or minus one

a) is ruled out because here delta l is zero

d) is ruled out becuase delta l is 2

c) is the only allowable transition that will emit a photon

Answer 2

Na - atomic number 11.

1s - 2 e-

2s - 2 e-

2p - 6 e-

3s - 1 e-

Stable state.

When a sodium atom gets excited, the electron furthest out jumps to the corresponding shell depending on the energy input. When it drops back down again to it's stable state (lowest energy state) - it emits a photon. Your answer is C - because 3s goes to 3p and then drops back down to 3s. Not only is this the correct answer, it is the only one that makes sense because the other shells definitely don't correspond and don't make any sense. I hope this helps.

Cheers.