The correct answer is Sulfur (S).
Sulfur has 6 valence electrons because it is located in Group 16 (or the sixth group over if you don’t count the transition metals). This means that one atom of sulfur has 6 electrons in its outermost shell out of 8 total “spots”, which you can count by counting the group numbers (excluding the transition metals) from Group 1 (with one valence electron) to Group 18 (the noble gases with full valence or outer shells).
By this same logic, Carbon (C) has 4 valence electrons and Cesium (Cs) has 1 valence electron, so neither of these is the correct answer.
Hope this helps!
I'm not sure what the question is asking, but the process would be considered endothermic (it absorbs heat)
Since the electron is de-exited from 1(st) exited state (i.e n=2) to ground state (i.e n=1) for first line of Lyman series. Since the atomic number of Hydrogen is 1. λ = 4/3⋅912 A. 1/R = 912 A
