As you go across a period, the nuclear charge will increase; the number of energy levels will stay the same, so there is a stronger and stronger attraction for the electrons. The electrons are being held more tightly as you go across a period. It becomes more and more difficult to lose electrons and consequently the reactivity of the metals decreases as you go from left to right across the periodic table. As you go down the periodic table, the nuclear charge increases but so does the number of shielding electrons. Consequently the dominant factor is that we have more and more energy levels and the electrons are further and further away from the nucleus. Thus it is easier for those electrons to come off.

Does this trend work for elements beyond the ones we have just looked at? You can check this out by taking a look at the reactions shown on a video tape called "Close-Up on Chemistry" by Julie and James Ealy produced by the American Chemical Society. It is available for you to look at on a monitor over in the lab.

E-mail instructor: Eden Francis Science Department 19600 South Molalla Avenue Oregon City, OR 97045 (503) 594-3352 TDD (503) 650-6649

Clackamas Community College
©1998, 2002 Clackamas Community College, Hal Bender