The properties of the elements are periodic functions of their atomic numbers.The periodic law tells us that if we arrange the elements in order of increasing atomic
number, we periodically encounter elements that have similar chemical and physical prop-
erties. The presently used “long form” of the periodic table (Table 4-2 and inside the
front cover) is such an arrangement. The vertical columns are referred to as groupsor
families,and the horizontal rows are called periods.Elements in a grouphave similar
chemical and physical properties, and those within a periodhave properties that change
progressively across the table. Several groups of elements have common names that are
used so frequently they should be learned. The Group IA elements, except H, are referred
to as alkali metals,and the Group IIA elements are called the alkaline earth metals.
The Group VIIA elements are called halogens,which means “salt formers,” and the
Group VIIIA elements are called noble(or rare) gases.
The general properties of metals and nonmetals are distinct. Physical and chemical
properties that distinguish metals from nonmetals are summarized in Tables 4-3 and 4-4.
Not all metals and nonmetals possess all these properties, but they share most of them to
varying degrees. The physical properties of metals can be explained on the basis of metallic
bonding in solids (Section 13-17).
Table 4-2, The Periodic Table, shows how we classify the known elements as metals
(shown in blue), nonmetals(tan), and metalloids(green). The elements to the left of those
Alkaline means basic. The character
of basic compounds is described in
Section 10-4.About 80% of the elements are metals.4-1 The Periodic Table: Metals, Nonmetals, and Metalloids 125TABLE 4-1 Predicted and Observed Properties of GermaniumEka-Silicon Germanium
Property Predicted, 1871 Reported, 1886 Modern Values
Atomic weight 72 72.32 72.61
Atomic volume 13 cm^3 13.22 cm^3 13.5 cm^3
Specific gravity 5.5 5.47 5.35
Specific heat 0.073 cal/g°C 0.076 cal/g°C 0.074 cal/g°C
Maximum valence* 4 4 4
Color Dark gray Grayish white Grayish white
Reaction with water Will decompose steam Does not decompose water Does not decompose
with difficulty water
Reactions with acids and Slight with acids; Not attacked by HCl or Not dissolved by HCl or
alkalis more pronounced dilute aqueous NaOH; H 2 SO 4 or dilute
with alkalis reacts vigorously NaOH; dissolved by
with molten NaOH concentrated NaOH
Formula of oxide EsO 2 GeO 2 GeO 2
Specific gravity of oxide 4.7 4.703 4.228
Specific gravity of 1.9 at 0°C 1.887 at 18°C 1.8443 at 30°C
tetrachloride
Boiling point of 100°C 86°C 84°C
tetrachloride
Boiling point of 160°C 160°C 186°C
tetraethyl derivative
*“Valence” refers to the combining power of a specific element.