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The periodic table is simply the organization and classification of different elements. By the end of the 1700 s, scientists had identified about 30 elements. In less than 100 years, the number of known element doubled because of new means of recognizing them. In the early 1800 s, Dobereiner observed that there were elements that could be classified into groups of 3, or triads.
These triads were significant because these classifications of similar elements represented the very beginning of the periodic table. The triads related atomic mass (in amu) to density. In 1865 a chemist named Newlands presented another way of classifying elements. In his time 62 elements were know. Newlands organized the elements in order of increasing atomic mass, and noticed that the properties of the first element were the similar to the eighth, the second to the ninth, and so on. He named this the law of octaves, as there are 8 notes in the musical scale. (octave to octave) The man most famous in relation to the periodic table, Dmitri Mendeleev, along with Lothar Meyer published tables almost identical of those to Newlands.
Mendeleev organized the elements in such a way as to make it easier for his students to understand. He eventually made the first actual periodic table of elements. This table had elements with similar properties in the same column. Mendeleev's table was so well designed and so accurate, that he was able to predict elements that had yet to be discovered with much precision. In 1913, Money discovered the concept of the atomic number. Even though Mendeleev's table was arranged by atomic mass, and now the periodic table is arranged by atomic number, why is Mendeleev's table valued so highly?
The first table is so important because the general rule is that as the atomic mass increases, so does the atomic number. Even though Mendeleev was organizing the elements the wrong way, his table is still incredibly similar to the present one. The periodic law is the basis for the periodic table. The periodic law states the following: When elements are arranged in order of increasing atomic number, their physical and chemical properties show a periodic pattern. The modern periodic table has one hundred and nine squares, each representing a unique element. Above the abbreviation of the element is the atomic number, and at the bottom of the square is the abbreviated electron configuration for the element.
Each element with similar properties is organized in to vertical columns called groups or families. The rows of the table are called periods. There are 7 periods and 18 groups. The groups of the periodic table are usually labeled with a roman numeral along with the letter A or B.
There has been controversy about whether or not to use Arabic numbers instead of the roman numerals, and it has still not been resolved. The textbook will use the Arabic numbers. In addition to the group labels, some are also given family names. Groups in 1 A are called alkali metals and the elements in 2 A are called the alkaline earth metals. 7 A is halogens, and 8 A is noble gases. Hydrogen is an exception to this rule, considering that it is definitely not an alkali metal.
Most squares in the periodic table are shaded a certain color. The light blue color that dominates the chart represents metals. Metals can be recognized by characteristics of luster or shine, are good conductors of heat and electricity, and are typically solids at room temperature, although mercury is an important exception. Most metals are malleable. Nonmetals are shaded a light red in the periodic table. The properties of these nonmetals vary greatly.
Some are solids at room temp, some gasses, but only one is a liquid. The third category in the periodic table, shaded purple, is the semi metals, or metalloid's. These elements have properties of both metals and nonmetals. Besides just the fact that the periodic table is ordered from smallest to largest atomic number, there is more thought in the logic than just that. The group number (such as 1 A) tells how many valence electrons there are in the atom.
All elements in group 1 A have one valence electron. The noble gas inner core refers to the nearest noble gas with a lower atomic number than the atom you are referring to. This is important because it is used in the abbreviation of the electron configurations. The shape of the periodic table has to do with the electron configurations. The s-block elements are groups 1 A and 2 A. In this block, the valence electrons are always in the s orbital.
The p-block elements have a maximum of 6 valence electrons. The d-block and f-block elements follow this same type of pattern. The confusing part has to do with how the electron configurations in the f-block to not progress sequentially from f 1 to f 14. This has to do with the quantum theory. The shape of the table is a result of the way electrons fill the s, p, d, and f orbitals of different energy levels.
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Research essay sample on Valence Electrons Periodic Table
