The Foundations of Chemistry

f-Transition Elements.Sometimes known as inner transition elements,these are elements
in which electrons are being added to forbitals. In these elements, the second from the
outermost occupied shell is building from 18 to 32 electrons. All are metals. The f-
transition elements are located between Groups IIIB and IVB in the periodic table.
They are

First f-transition series (lanthanides): 58 Ce through 71 Lu

Second f-transition series (actinides): 90 Th through 103 Lr

The A and B designations for groups of elements in the periodic table are somewhat
arbitrary, and they are reversed in some periodic tables. In another designation, the groups
are numbered 1 through 18. The system used in this text is the one commonly used in
the United States. Elements with the same group numbers, but with different letters, have
relatively few similar properties. The origin of the A and B designations is the fact that
some compounds of elements with the same group numbers have similar formulas but
quite different properties, for example, NaCl (IA) and AgCl (IB), MgCl 2 (IIA) and ZnCl 2
(IIB). As we shall see, variations in the properties of the B groups across a row are not
nearly as regular and dramatic as the variations observed across a row of A group elements.

The outermostelectrons have the greatest influence on the properties of elements.

Adding an electron to an inner dorbital results in less striking changes in proper-

ties than adding an electron to an outer sor porbital.

PERIODIC PROPERTIES OF THE ELEMENTS

Now we investigate the nature of periodicity. Knowledge of periodicity is valuable in
understanding bonding in simple compounds. Many physical properties, such as melting
points, boiling points, and atomic volumes, show periodic variations. For now, we describe
the variations that are most useful in predicting chemical behavior. The variations in these
properties depend on electron configurations, especially the configurations in the outer-
most occupied shell, and on how far away that shell is from the nucleus.

6-1 More About the Periodic Table 239

The elements of Period 3.

Properties progress (left to right)

from solids (Na, Mg, Al, Si, P, S) to

gases (Cl, Ar) and from the most

metallic (Na) to the most

nonmetallic (Ar).

In any atom the outermostelectrons are

those that have the highest value of the

principal quantum number, n.

http://webbook.nist.gov

See the Saunders Interactive

General Chemistry CD-ROM,

Screen 8.9, Atomic Properties and

Periodic Trends.