orbitals fill.) The sixth period follows much the same pattern and has the filling
order 6s^2 , 4f^14 , 5d^10 , 6p^6. Here, again, irregularities occur and can best be
followed by using Table 3.
The vertical columns of the Periodic Table are called groups or families.
The elements in a group exhibit similar or related properties. In 1984 the IUPAC
agreed that the groups would be numbered 1 through 18.
PROPERTIES RELATED TO THE PERIODIC TABLE
Metals are found on the left of the chart (see Table 4) with the most active metal
in the lower left corner. Nonmetals are found on the right side with the most
active nonmetal in the upper right-hand corner. The noble or inert gases are on the
far right. Since the most active metals react with water to form bases, the Group 1
metals are called alkali metals. As you proceed to the right, the base-forming
property decreases and the acid-forming properties increase. The metals in the
first two groups are the light metals, and those toward the center are heavy metals.
The elements found along the dark line in the Periodic Table (Table 4) are
called metalloids. These elements have certain characteristics of metals and other
characteristics of nonmetals. Some examples of metalloids are boron, silicon,
arsenic, and tellurium.
Here are some important general summary statements about the Periodic
Table:
■ Acid-forming properties increase from left to right on the table.
■ Base-forming properties are high on the left side and decrease to the right.
■ The atomic radii of elements decrease from left to right across a period.
■ First ionization energies increase from left to right across a period.
■ Metallic properties are greatest on the left side of the table and decrease to
the right.
■ Nonmetallic properties are greatest on the right side of the table and
decrease to the left.TIP
These are important trends to remember.Study Table 4 carefully because it summarizes many of these properties. For
a more detailed description of metals, alloys, and metalloids see pages in Chapter
13.