Certain characteristics follow trends going across rows or down columns in the periodic table. Moving to the right across a single row of the table, any one electron experiences more of an attraction to the nucleus because the nucleus contains more positive charges. Therefore, the electrons are more tightly bound to the nucleus toward the right of the row. This result implies that the size (radius) of an atom decreases moving from left to right. Traveling down a column means adding more shells of electrons, so the size of the atom must necessarily increase.
The elements of the periodic table can be classified into three main groups: metals, semimetals or metalloids, and nonmetals. In addition, certain columns of the periodic table have recognizable features.
A dividing line exists in the periodic table beginning between boron and aluminum and proceeding stepwise down to the right (i.e., passing next between aluminum and silicon and then between silicon and germanium). Metals are those elements found to left of this line, nonmetals are on the right of this line, with the semimetals or metalloids lying adjacent to the line. Metals are generally malleable (easily shaped), ductile (easily pulled into wire), good conductors, and lustrous. Nonmetals are generally brittle and poor conductors. Their other characteristics vary more than those of metals.
