Modern Periodic TableModern Periodic Table

Father of the Modern Periodic TableFather of the Modern Periodic TableDmitri MendeleevDmitri Mendeleev

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

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

1.1. The elements, if arranged according to their The elements, if arranged according to their atomic atomic

weightsweights, exhibit cyclical repetition of , exhibit cyclical repetition of propertiesproperties..

2. Elements that are similar in 2. Elements that are similar in chemical propertieschemical properties

have atomic weights that are either the same have atomic weights that are either the same valuevalue

(e.g.Pt, Ir, Os) or which (e.g.Pt, Ir, Os) or which increase regularlyincrease regularly (e.g. K, (e.g. K,

Ru, Cs).Ru, Cs).

3. The arrangement of elements or groups of 3. The arrangement of elements or groups of

elements in the order of their atomic weights, elements in the order of their atomic weights,

correspond to their distinctive chemical correspond to their distinctive chemical

properties (e.g. Li, Be Ba, C, N, 0, and Sn).properties (e.g. Li, Be Ba, C, N, 0, and Sn).

4. The elements that have the least density have 4. The elements that have the least density have

the the smallestsmallest atomic weights. atomic weights.

55. . The size of the atomic weight determines The size of the atomic weight determines

the the charactercharacter of the element. of the element.

6. 6. We should expect the discovery of We should expect the discovery of yet yet

unknownunknown elements (e.g. elements related elements (e.g. elements related

to aluminium and silicon whose atomic to aluminium and silicon whose atomic

weight would be between 65 and 75).weight would be between 65 and 75).

7. The atomic weight of an element may be 7. The atomic weight of an element may be

determined by a knowledge of elements determined by a knowledge of elements

which which neighbor itneighbor it. Thus the atomic weight of . Thus the atomic weight of

tellurium must lie between 123 and 126, and tellurium must lie between 123 and 126, and

cannot be 128.cannot be 128.

8. Certain characteristic properties can be 8. Certain characteristic properties can be

predictedpredicted from their from their atomic weights.atomic weights.

On November 29, 1870, Mendeleev took this On November 29, 1870, Mendeleev took this concept even further by stating that it was concept even further by stating that it was possible to predict the properties of possible to predict the properties of undiscovered elements. undiscovered elements.

He then proceeded to make predictions for He then proceeded to make predictions for three new elements (eka - aluminium, eka-three new elements (eka - aluminium, eka-boron, and eka-silicon) and suggested several boron, and eka-silicon) and suggested several properties of each, including atomic mass, properties of each, including atomic mass, density, radii, and combining ratios with density, radii, and combining ratios with oxygen. The science world was perplexed, and oxygen. The science world was perplexed, and many scoffed at Mendeleev's predictions. many scoffed at Mendeleev's predictions.

It was not until November 1875 when the It was not until November 1875 when the Frenchman Lecoq de Boisbaudran Frenchman Lecoq de Boisbaudran discovered one of the predicted elements discovered one of the predicted elements (eka-aluminium) which he named gallium (eka-aluminium) which he named gallium caused Dmitri's ideas to be taken caused Dmitri's ideas to be taken seriously. seriously.

The other two elements were discovered The other two elements were discovered later and their properties were found to be later and their properties were found to be remarkably similar to those predicted by remarkably similar to those predicted by Mendeleev. These discoveries, verifying Mendeleev. These discoveries, verifying his predictions and substantiating his law, his predictions and substantiating his law, took him to the top of the science world.took him to the top of the science world.

Mendeleev’s tableMendeleev’s table

We know of many elements now…We know of many elements now…

The Modern Periodic TableThe Modern Periodic Table

The modern periodic table is a The modern periodic table is a classification system that applies to the classification system that applies to the elements. elements.

The arrangement of the elements in this The arrangement of the elements in this table allows us to group elements with table allows us to group elements with common common chemical and physical properties, chemical and physical properties, as well as common atomic structure.as well as common atomic structure.

The Modern Periodic Table The Modern Periodic Table page 17 in notespage 17 in notes

Each square in the periodic table Each square in the periodic table represents represents one elementone element and contains a and contains a large amount of information about that large amount of information about that element. element.

The Modern Periodic TableThe Modern Periodic Table

The elements are then arranged in a table The elements are then arranged in a table as follows.as follows.

The horizontal rows of the table are The horizontal rows of the table are referred to as referred to as periodsperiods..

All elements in these rows have the same All elements in these rows have the same number of number of energy levels in which electrons energy levels in which electrons are found.are found.

The vertical columns of the table are The vertical columns of the table are referred to as referred to as groups, or familiesgroups, or families, of , of elements.elements.

Elements in these columns share similar Elements in these columns share similar physical and chemicalphysical and chemical characteristics. characteristics.

Classification of the ElementsClassification of the Elements

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

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

Group 1 Alkali Metals

Alkaline Earth MetalsAlkaline Earth Metals

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

Group 2 Alkaline Earth Metals

Transition MetalsTransition Metals

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

Group 3 -12 Transition Metals

LanthanidesActinides:

HalogensHalogens

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

Group 17 Halogens

Noble Gases:Noble Gases:

Elements belonging to Group 18. Elements belonging to Group 18.

These elements are very un-reactive, however, These elements are very un-reactive, however, they are not nonreactive as compounds they are not nonreactive as compounds containing these elements have been containing these elements have been synthesized. There are no naturally occurring synthesized. There are no naturally occurring compounds that are made up of these elements.compounds that are made up of these elements.

Group 18 Noble Gases

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