121 / 123
BananaStock/Getty Images
APPLY SCIENTIFIC PRINCIPLES
AND EVIDENCE
Explain how a discovery about an element or elements
was incorporated into the modern periodic table.
C
C
C
S
E
P
D
C
I
The Evolving Periodic Table
The Adaptable Periodic Table
The design of the periodic table that we use
today was developed in the 19th century, before
the discovery of all of the naturally occurring
elements, including the noble gases, and before
the synthesis of elements. Initially, the elements
were organized on the periodic table by atomic
mass. This caused some inconsistencies. Once
the atomic number was used to align the
elements into rows and properties were used to
organize the elements into columns, the mod-
ern periodic table was born.
The modern periodic table demonstrates the
elegance of the nature of science. The early
periodic table evolved to incorporate new
information. For example, a new column was
added when the noble gases were discovered.
Period 7 is now completely filled after the
recently discovered elements 113, 115, 117, and
118 were added.
Newly synthesized elements must now be
added to another row. If and when these new
elements are discovered, period 8 will be
added to the periodic table.
When the periodic table was being developed
chemists did not understand why these groups
of elements had similar properties, but they
recognized the periodic trend in these proper-
ties. Today, students and chemists understand
that elements in a group have similar properties
and the same number of valence electrons. Our
understanding of the atom evolved along with
our understanding of what elements in a group
on the periodic table have in common in terms
of valence electrons, reactivity, and properties.
While the nature of atoms and elements were
not understood at the time of the periodic
table’s development, the original table was
well designed. As new information was
discovered about atoms and elements, the
periodic table evolved and incorporated the
new information resulting in a table that is just
as useful today as it was when it was first
developed.
Chemists have used the periodic table since
its development in the late 1860s, but it has
evolved over the years, and it is still evolving
today.
The periodic table has evolved since it was developed in
the 1800s, but it still remains an important fixture in
chemistry classrooms today.
NATURE OF SCIENCE
Module 5 • Nature of Science
161
CALIFORNIA CONNECTION
Californium was discovered in 1950 and named after
California. Conduct research to find out more about
californium and its applications.