Which of the following lists the given elements in order of decreasing first ionisation energies?
[Atomic numbers: Li=3, Be = 4, Na = 11]
A. Be, Li, Na is the answer, can someone explain why?
Doesn’t the exception of ionisation energy regards to ‘When in same period, Group 5A > Group 6A’?
The Ionization Energy trend decreases as you go to the left of the period and down a group. Therefore, the least will be Na, Be will be the highest among these elements, and Li in the middle.
The exception - about ionisation energy dropping between group 5 and 6 is still true though! Just the elements involved in this question don’t involve those two groups so its just not relevant to the question.