Question

Consider these 3 transitions for an electron in a hydrogen atom.  
I) n = 7 --> n = 1    II ) n = 7 --> n = 5    III ) n = 1 --> n = 7     IV) n = 7 --> n = 6.  
Which of these has a negative ΔE?

		I only
		III and IV
		II only
		I and III
		I and II
		IV only
		I, II and IV
		I, II , III , and IV

Answer 1

Solution:- Energy is required if the electron goes from lower energy level to higher energy level and it is released if the electrons falls from higher energy level to lower energy level.

Energy requirde means endothermic reaction and so the sign would be positive. Energy released means exothermic reaction and so the sign would be negative. in I, II and IV, electrons is falling from higher energy level to lower energy level where as in III, it's going from lower to higher energy level.

So, the sign of delta E would be negative for I, II, and IV and the right choice is 7th.