The periodic table can not only depiet the objecive law of the element periodic law quite well, but also fully reprcsent main group element in close relationship with subgroup clement, thus expressing the duality of cach element.

• 该表不仅能很好地反映出元素周期律的客观规律,而且能充分地体现出主族元素和副族元素之间的密切联系,从而表达出每个元素的两重性。