Ionization Energy (eV)
		0	+	2+	3+	4+	5+	6+
		I	II	III	IV	V	VI	VII
	H	13.6
	He	24.6	54.4
	C	11.3	24.4	47.9	64.5
	N	14.5	29.6	47.4	77.5	97.9
	O	13.6	35.1	54.9	77.4	113.9	138.1
	Ne	24.6	41.0	63.4	97.2	126.2
	Na	5.1	47.3	71.6	98.9	138.4
	Mg	7.6	15.0	80.1
	Al	6.0	18.8	28.4
	S	10.4	23.3	34.9
	Ar	15.8	27.6	40.7	59.6	74.8
	Ca	6.1	11.9	50.9	67.3	84.3
	Fe	7.9	16.2	30.7	54.9	75.0	99.0	125.0
	Si	8.1	16.3	33.5	45.1	166.8
	F. Teyssier				Vertical lines : H I - He I - He II
	www.astronomie-amateur.fr
	Source :
	Kramida, A., Ralchenko, Yu., Reader, J., and NIST ASD Team (2014). NIST Atomic Spectra Database (ver. 5.2), [Online]. Available: http://physics.nist.gov/asd [2016, July 31]. National Institute of Standards and Technology, Gaithersburg, MD.