Rb has the least
Rb
The Pauling electronegativity and the first ionization energy increase from sodium to chlorine.
The ionization energy increase from sodium to fluorine.
You are referring to the ionization enthalpy. The first ionization energy of sodium is the energy for the process Na(g) --> Na+(g) + e-(g).
Na, sodium, should have the lowest first ionization energy of those four elements.
Lithium has the least number of protons, rubidium has the most number of protons.
Potassium
K (lowest) Na Li B N (highest)
I'm assuming you're referring to the problem Na(g)+Cl(g) -> Na+(g)+Cl-(g)Since, ionization energy is basically the amount of energy it takes to dislodge one electron from a neutral atom, Cl has to dislodge one electron to stabilize NaThus,Na -> Na++e-
Na, sodium
The order is: Cl,S, Si, Al, Na.
Na(g) --> Na+(g) + e- First ionisation energy is always: X(g) --> X+(g) + e- with X being an element