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Solving Problems: A Chemistry Handbook
Chemistry: Matter and Change
53
The Periodic Table and
Periodic Law
The Periodic Table and
Periodic Law
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER
6
6.1 Development of the Modern Periodic Table
In 1869, the Russian chemist Dmitri Mendeleev noted that when the
known elements were placed in order of increasing atomic mass,
their properties repeated in a regular pattern—a periodic pattern.
Mendeleev made a table in which he arranged the elements in order
of increasing atomic mass into columns with similar properties.
From his table, Mendeleev predicted the properties of three elements
that were undiscovered at the time. When these elements—scandium, gallium, and germanium—were soon discovered and found to
have most of the predicted properties, Mendeleev’s periodic table
was accepted in the scientific world. Besides the addition of newly
discovered elements, the only major change in the organization of
the periodic table since Mendeleev’s time is that the elements are
now arranged in order of atomic number instead of atomic mass.
The modern periodic table Study the modern periodic table
that appears in your textbook on pages 178–179. Each square gives
certain information about each element, as shown in the following
diagram.
Hydrogen
1
H
1.008
Element
Atomic number
Symbol
Atomic mass
State of matter
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