Which row shows the elements in order of increasing first ionisation energy?
Rb<Ca<Si<N\text{Rb} < \text{Ca} < \text{Si} < \text{N}Rb<Ca<Si<N
N<Si<Ca<Rb\text{N} < \text{Si} < \text{Ca} < \text{Rb}N<Si<Ca<Rb
Rb<Si<Ca<N\text{Rb} < \text{Si} < \text{Ca} < \text{N}Rb<Si<Ca<N
Ca<Rb<Si<N\text{Ca} < \text{Rb} < \text{Si} < \text{N}Ca<Rb<Si<N
