is nitrogen has greater ie1 than chlorine

Chlorine has the electronic configuration of [Ne]3s23p5

The effective nuclear charge is 7, the same as fluorine. Predicting the ionization energy would be difficult with this alone. The atomic size, however, is larger for chlorine than for fluorine because now there are three energy levels (chlorine is in Period 3). Now we can say that the ionization energy should be lower than that of fluorine because the electron would be easier to pull off the level further away from the nucleus. (Indeed, the value for chlorine is 1251 kJ/mol).