In general for any many electron atom any particular electron will always be screened from the nucleus to some extent by the remaining electrons. The difference between the full nuclear charge z and the screening effect of the inner two electrons is called the effective nuclear charge or z eff. There is a nice excel spreadsheet that allows you to.
There are many properties for which you can investigate periodic trends. Relate these trends to effective nuclear charge and atomic size. Sketch a periodic table indicating the trend of electronegativities from lowest to highest.
Moving from top to bottom down a column of the periodic table we might expect the elements to have a similar effective nuclear charge as they all have the same number of valence electrons. This results in a trend that in general the effective nuclear charge increases from left to right across any period of the periodic table. Effective nuclear charge and periodic trends now we have learned that core electrons shield outer electrons from the nuclear charge let s now take this knowledge to predict periodic trends.
Notice that at the beginning of each new period the effective nuclear charge drops significantly almost back to the beginning value of the period before it. The noble gases are labeled and designate the highest effective nuclear charge values for each row. The graph below illustrates this overall periodic table trend.
Therefore as we go from left to right on the periodic table the effective nuclear charge of an atom increases in strength and holds the outer electrons closer and tighter to the nucleus. We can see from equation ref 4 that the effective nuclear charge of an atom increases as the number of protons in an atom increases figure pageindex 2.
