Modern Periodic Table

Father of the Modern Periodic Table Dmitri Mendeleev In the middle of 1800's there was a great deal of interest in the study of elements. Within 60 years the number of known elements increased from 26 to 62. Scientists realized that some of the elements exhibited similar chemical and physical properties and many attempts were made to organize the known elements in a table so that elements with similar properties would occur within the same row. In 1866, Newlands published a relationship of the elements entitled the "Law of Octaves". Unfortunately, the heavier elements did not fit well unto his theory.

Mendeleev's ideas were similar to those of Newlands but Dmitri had more data and felt that Newlands had not gone far enough in his research. By 1869, the Russian chemist had assembled detailed descriptions of more than 60 elements and, on March 6, 1869 a formal presentation was made to the Russian Chemical Society entitled "The Dependence Between the Properties of Atomic Weights of the Elements." Unfortunately, Mendeleev was ill and his colleague Professor Menshutken gave the presentation. There were eight points to his presentation.

The elements, if arranged according to their atomic weights, exhibit cyclical repetition of properties. 2. Elements that are similar in chemical properties have atomic weights that are either the same value (e.g.Pt, Ir, Os) or which increase regularly (e.g. K, Ru, Cs).

3. The arrangement of elements or groups of elements in the order of their atomic weights, correspond to their distinctive chemical properties (e.g. Li, Be Ba, C, N, 0, and Sn). 4. The elements that have the least density have the smallest atomic weights.

5. The size of the atomic weight determines the character of the element. 6. We should expect the discovery of yet unknown elements (e.g. elements related to aluminium and silicon whose atomic weight would be between 65 and 75).

7. The atomic weight of an element may be determined by a knowledge of elements which neighbor it. Thus the atomic weight of tellurium must lie between 123 and 126, and cannot be 128. 8. Certain characteristic properties can be predicted from their atomic weights.

On November 29, 1870, Mendeleev took this concept even further by stating that it was possible to predict the properties of undiscovered elements. He then proceeded to make predictions for three new elements (eka - aluminium, eka-boron, and eka-silicon) and suggested several properties of each, including atomic mass, density, radii, and combining ratios with oxygen. The science world was perplexed, and many scoffed at Mendeleev's predictions.

It was not until November 1875 when the Frenchman Lecoq de Boisbaudran discovered one of the predicted elements (eka-aluminium) which he named gallium caused Dmitri's ideas to be taken seriously. The other two elements were discovered later and their properties were found to be remarkably similar to those predicted by Mendeleev. These discoveries, verifying his predictions and substantiating his law, took him to the top of the science world.

Mendeleev’s table

We know of many elements now…

The Modern Periodic Table The modern periodic table is a classification system that applies to the elements. The arrangement of the elements in this table allows us to group elements with common chemical and physical properties, as well as common atomic structure.

The Modern Periodic Table page 17 in notes Each square in the periodic table represents one element and contains a large amount of information about that element.

The Modern Periodic Table The elements are then arranged in a table as follows. The horizontal rows of the table are referred to as periods. All elements in these rows have the same number of energy levels in which electrons are found.

The vertical columns of the table are referred to as groups, or families, of elements. Elements in these columns share similar physical and chemical characteristics.

Classification of the Elements Elements can be classified into very distinct groups based upon their chemical and physical characteristics.

Alkali Metals: metals in the first column or Group 1 of the periodic table (i.e. lithium, sodium, potassium, rubidium, cesium, and francium). With the exception of francium, these metals are all soft and silvery. These elements react vigorously, even violently, with water and must be stored in oil to prevent contact with the moisture in the air. These elements are never found in their pure form naturally. Group 1 Alkali Metals

Alkaline Earth Metals Elements in the second column or Group 2 of the periodic table all fall into these, series. These elements are in general white, differing by shades of colour; they are malleable, extrudable and machinable. These elements may be made into rods, wire or plate. These elements are less reactive than the alkali metals. When the surface of these metals comes in contact with oxygen in the air, a strong protectiveoxide coating is formed. This coating must be removed for further reaction to occur Group 2 Alkaline Earth Metals

Transition Metals This series includes all elements in Groups 3-12 and the sub-series Lanthanides and Actinides (inner transition metals). In general these elements are known for their hardness, high density, high melting and boiling points and heat conduction although there are exceptions. Some of these elements form coloured ions. Group 3 -12 Transition Metals Lanthanides Actinides:

Halogens The reactive non-metals in Group 17 of the periodic table. These elements are so reactive that they are never found as elements in nature. Group 17 Halogens

Noble Gases: Elements belonging to Group 18. These elements are very un-reactive, however, they are not nonreactive as compounds containing these elements have been synthesized. There are no naturally occurring compounds that are made up of these elements. Group 18 Noble Gases

In your learning groups.. An Elemental Tale Assignment Understanding Matter – Periodicity of Elements Assignment