Why does it generally decrease as you go from left to right across a row on the periodic table??
2007-01-31 16:57:45 · 3 answers · asked by Tracey Lee ♥ 2 in Science & Mathematics ➔ Chemistry
As you go across a period, the nuclear charge increases and the number of energy levels stays the same. Consequently, the number of shielding electrons stays the same and the effective nuclear charge increases. As the effective nuclear charge increases, it pulls the electrons in closer and closer to the nucleus. So as you go across a period, the increase in the nuclear charge causes a decrease in the atomic size because the electrons in the valence energy level are pulled in closer and closer.
2007-01-31 17:17:43 · answer #1 · answered by originalsmartie 4 · 1⤊ 0⤋
In the periodic table, atomic radii increase down a group as new electron shells are added, and decrease left-to-right as the nuclear charge (or number of protons) is increased - an important exception are the noble gases.
2007-01-31 17:23:23 · answer #2 · answered by 13angus13 3 · 0⤊ 0⤋
the elements are arrranged in such a way that they are in increasing atomic number and weight, number of valences, and decreasing radius
2007-01-31 17:44:18 · answer #3 · answered by probug 3 · 0⤊ 0⤋