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No Communication
Chemists couldn't communicate, there was much confusion, because there was no method for accurately determining an element's atomic mass or the number of atoms of an element in a particular chemical compound. -
Period: to
Development of the Periodic Table
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Meeting
Chemists met up in Germany and held the first International Congress of Chemists Meeting to decide a convincing method for accurately measuring the relative masses of atoms. -
Importance of this Achievement
This enabled scientists to agree on standard value for atomic mass and inititated a search for relationships between atomic mass and other properties of the elements. -
Dmitri Mendeleev
He noticed that when the elements were arranged in order of increasing atomic mass, certain similarities in their chemical properties appeared at regular intervals. This shows how elements belonging to a group of the periodic table are interrelated in terms of atomic number. His principle of chemical periodicity is correctly stated in what is known as the periodic law. -
Periodic Law
The physical and chemical properties of the elements in order of their atomic numbers so that elements with similar properties fall in the same column, or group. -
Group
A vertical column of elements in the periodic table. -
Predict Properties of Elements
The periodic law can be used to predict the physical and chemical properties of elements from left to right, by atomic number. Elements that are close together on the periodic table have similar properties. -
Period
A horizontal row of elements in the periodic table. -
Henry Moseley
Moseley's work led to both the modern definition of atomic number and the recognition that atomic number, not atomic mass, is the basis for the organization of the periodic table. Moseley's discovery was consistent with Mendeleev's ordering of the periodic table by properties rather than strictly by atomic mass. -
Different States of Elements
There are elements that are in gaseous forms, liquids, solids, and some are synthetic, or "man-made." -
Metals
There are different types of Metals: Alkali Metals, Alkaline Earth Metals, Transition Metals, and some other Metals. Metals are elements that are good conductors of heat and electricity. -
Nonmetals
There are different types of Nonmetals: Halogens, Noble Gases, Lanthanides, Actinides, and other Nonmetals. Nonmetals are elements that are poor conductors of heat and electricity. -
Metalloids
Metalloids or Semiconductors are elements that have some characteristics of metals and some characteristics of nonmetals. -
Element 113
This element was discovered a about 3 years ago, but was officially added to the periodic table about 3 weeks ago. The name has yet to be decided. -
Modern Periodic Table Organization
An arrangement of the elements in order of their atomic numbers so that elements with similar properties fall in the same column, or group. It's about change and progress of the new development.
