The elements of the periodic table show trends. Trends can be recognized by using the periodic table and can be explained by analyzing the electron configuration of the elements. Elements gain or lose valence electrons to obtain stable octet formation. Stable octets are seen in the noble gases of Group VIII of the periodic table. There are two other important trends. The first is, electrons are added one at a time moving from left to right across a period. The electrons of the outermost shell experience increasingly strong nuclear attraction, so the electrons become closer to the nucleus and more tightly bound to it. Second, moving down a column in the periodic table, the outermost electrons become less tightly bound to the nucleus. These trends explain the periodicity observed in the elemental properties of atomic radius, ionic radius, electron affinity, and electronegativity.
