Bibliography
http://www.ausetute.com.au/trendpd3.html
http://www.webelements.com/
http://www.chemicool.com/elements/
http://chemistry.about.com/od/periodicitytrends/a/ionization-energy.htm
http://www.chem.tamu.edu/class/majors/tutorialnotefiles/trends.htm
http://www.webelements.com/
http://www.chemicool.com/elements/
http://chemistry.about.com/od/periodicitytrends/a/ionization-energy.htm
http://www.chem.tamu.edu/class/majors/tutorialnotefiles/trends.htm