One of the major sources of information that the student account of Biotechnology, Chemistry and Biochemistry is the periodic table. Here the elements are classified based on the similarity of their properties, which repeated at regular intervals are called periodic properties.
The structure of the periodic table the proposals is due to Mendeleev, Meyer and Moseley, as well as A. Warner. In analyzing the periodic table the elements are ordered increasingly from its atomic number, divided into periods and groups, both horizontally and vertically, respectively. In addition, points out what metals, nonmetals, transition metals and other groups of elements known as rare earths.
The periodic table is a ranking of the 109 known chemical elements present, in order of increasing atomic number. There were several attempts that were made from 1817 to 1914 and more recently still, to classify elements.
The classification of elements based on atomic number resulting in the modern periodic table of Alfred Werner. This table contains all the elements found in nature as well as those obtained under laboratory conditions, and are arranged according to the electronic structure of atoms, showing a gradual accommodation of the valence electrons in energy levels {periods }. The elements have similar outer electron configurations, grouped in vertical columns are called families or groups.
also that the elements are located in the periodic table in ascending order, based on atomic number and, consequently, its electronic configuration, we can tell that it is also located kinds of elements, periods, groups or families and blocks.
classes of items.
When items are classified according to their physical and chemical characteristics, forming two main groups: metals and nonmetals. There is also a third set of elements that are characterized by the uncertainty of its properties located between metals and nonmetals, called metalloids or semimetals.
Metals Metals are recognized by their physical properties, such as metallic luster, electrical and thermal conductivity, hardness, ductility and malleability. In metals the same period is more reactive which has fewer electrons in its outer shell. Compared to sodium and aluminum, found in the second period, the more reactive sodium because it has a valence electron and aluminum has three, it is easier to give an electron to two or more. Na11
2P6 1s2 2s2 3s1 outer layer 1 valence electron
Al13 1s2 2s2 3s2 3p1 2P6 outer layer 3 valence electrons
Nonmetals Nonmetals are elements that tend to gain electrons to complete its outer shell with eight and thus achieve a stable configuration of noble gas. Are more reactive the lowest number atomic, because in this case the distance between the nucleus and the electrons of the last orbit is lower and, or both, the attraction of the nucleus to the electrons of other elements is greater. Thus, in the group of the most reactive halogen is fluorine, atomic number 9, and the less reactive is iodine, atomic number 53, because although both have seven electrons in its valence shell, the fluor are attracted more strongly, by being closer to the core, that iodine, which are at level five. Metalloids
The elements boron, silicon, germanium, arsenic, antimony, tellurium and polonium, which are above and below of the ladder line that divides metals from nonmetals are called metalloids because their properties are intermediate between metals and nonmetals, for example, conduct electricity, but not so much metal.
periods long
The periodic table is composed of seven periods, arranged horizontally from 1 to 7. These numbers correspond to the energy levels of the atom, where electrons are located. The number of the period where it is located an item indicates the maximum level of energy in the atom of that element will have electrons, for example, iron (iron) is located in period 4, which is the maximum power level which has electrons. Fe26
2P6 1s2 2s2 3s2 4s2 3p6 3d6
maximum electron energy level
In the first three periods are called short periods, and the remaining four long periods. The following table shows the number of elements that make up each period.
periods (energy levels) No. of items sublevels Ends Begins in
February 1 H He Li 1s Ne
August 2 August 3
2s 2p 3s 3p Na Ar K
April 18 Kr 4s 3d 4p Rb
May 1918 Xe 5s 4d 5p
June 1932 Rn Cs 6s 4f 5d 6p Fr Une
July 23 5f 7s 6d periods
Features
As you can see in the periodic table, the seventh period, which begins with France, has empty places for new items that are expected to have properties similar to those of the group elements corresponding to them.
Groups or families are a set of elements with similar properties. Are arranged in vertical columns and are identified by Roman numerals I through VIII. They are divided into groups A and B. For the elements of groups A, the IA to VIIA is called representative elements, and group B, the transition elements.
Description of groups or families
Group IA elements belonging to this group are known as alkali metals. All are soft and bright (except for hydrogen, which is a non metal), highly reactive with air and water, hence, are not free in nature and when able to isolate, to avoid reacting, must be kept submerged in certain liquids such as oils or petroleum ether. React with VIIA group elements form ionic compounds.
Its outer electron configuration is (ns1), tend to lose this electron and stay with oxidation number + 1. These metals are more electropositive. Francium is the last element of this group is radioactive.
In the periodic table hydrogen is placed in this group due to single electron who owns it is a gaseous element and its properties are not the same as the rest of the alkali metals. 1H
3Li 11Na 37Rb 19K 56Cs 87Fr
Group IA IIA
Group have certain properties similar to alkali metals, but are a little less reactive and they are known as alkaline earth metal. With oxygen in the air form oxides and react with the elements of group VIIA (halogen) to form salts.
have completed his orbital s in its outer shell (ns2) and tend to lose these electrons taking the noble gas configuration above them, hence, its oxidation number is +2.
The reactivity of these metals increases as you move from top to down on the group: for example, beryllium and magnesium react with oxygen to form oxides only at elevated temperatures, while calcium, strontium and barium do at room temperature. The radio, as well as France, the former group, is a radioactive element. Group IIA 4BE
12mg 20Ca 38Sr 56Ba 88Ra
IIIA
Group This group is composed of boron, aluminum, gallium, indium and thallium. Boron is a metalloid, and the four remaining metallic elements, perhaps the most important properties and abundance is aluminum, which when combined with oxygen, forms a cover which prevents any further reaction, which is why this metal is used in the preparation of articles and structural materials. The outer electron configuration is presented (ns2 np1). These elements also form molecular compounds, which are characteristic of non-metals, this is explained by the electronic configuration and its present location in the table, as they move from left to right in the periodic table, the metallic nature of representative elements gradually begins to lose. 5B
13Al Group IIIA 31Ga 49In 81Tl
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