I have come across the Slater's Rules that is used to calculate the numerical value of effective nuclear charge of elements. Can somebody please show to me the calculation of effective nuclear charge of atoms of element down the group 2 by using the Slater's rule?? I calculate by using the information from http://en.wikipedia.org/wiki/Slater's_rules. many books mention that increment in atomic radius down the group 2 is caused by the decreasing effective nuclear charge. is it true? Thanks for your help and i really need all your help.