The Foundations of Chemistry

General trends in metallic character

of A group elements with position in

the periodic table.

4-1 The Periodic Table: Metals, Nonmetals, and Metalloids 127

touching the heavy stairstep line are metals (except hydrogen), and those to the right are
nonmetals. Such a classification is somewhat arbitrary, and several elements do not fit
neatly into either class. Most elements adjacent to the heavy line are often called metal-
loids (or semimetals), because they are metallic (or nonmetallic) only to a limited degree.

Metallic characterincreases from top to bottom and decreases from left to right with

respect to position in the periodic table.

Cesium, atomic number 55, is the most active naturally occurring metal. Francium and
radium are radioactive and do not occur in nature in appreciable amounts. Noble gases
seldom bond with other elements. They are unreactive, monatomic gases. The most active
nonmetal is fluorine, atomic number 9.

Nonmetallic characterdecreases from top to bottom and increases from left to right

in the periodic table.

Metalloids show some properties that are characteristic of both metals and nonmetals.
Many of the metalloids, such as silicon, germanium, and antimony, act as semiconductors,
which are important in solid-state electronic circuits. Semiconductorsare insulators at
lower temperatures, but become conductors at higher temperatures (Section 13-17). The
conductivities of metals, by contrast, decrease with increasing temperature.
Aluminum is the least metallic of the metals and is sometimes classified as a metalloid.
It is metallic in appearance, and an excellent conductor of electricity.
In this and later chapters we will study some chemical reactions of elements and their
compounds and relate the reactions to the locations of the elements in the periodic table.
First, we will describe some important properties of solutions and what they tell us about
the nature and behavior of the dissolved substances, the solutes.

TABLE 4-4 Some Chemical Properties of Metals and Nonmetals

Metals Nonmetals

1.Outer shells contain few electrons— 1.Outer shells contain four or more
2.usually three or fewer 2.electrons*
2.Form cations (positive ions) by losing 2.Form anions (negative ions) by gaining
2.electrons 2.electrons†
3.Form ionic compounds with 3.Form ionic compounds with metals†and
2.nonmetals 2.molecular (covalent) compounds with other
2.nonmetals

4.Solid state characterized by metallic 4.Covalently bonded molecules; noble
2.bonding 2.gases are monatomic

*Except hydrogen and helium.
†Except the noble gases.

Aluminum is the most abundant metal

in the earth’s crust (7.5% by mass).

Silicon, a metalloid, is widely used in

the manufacture of electronic chips.

Decrease

IncreaseMetallic character Increase