Some nature of the periodic elements

Periodic properties of elements are properties that change uniformly in accordance with the increase of atomic number elements. Periodic properties of elements associated with the electron structure of elements. Periodic properties of elements including the atomic radius, ionization energy, electron affinity, and electronegativity.

1. Atomic Radius
atomic radius is the distance from the center core to the outermost electron. Atomic radius is determined by measuring the bond length (distance between the nuclei) in covalent compounds, such as the Cl-Cl or H-H and then dividing by two. Therefore, the radius of an atom is often called the covalent radius.
Atomic radius varies depending on the size terikan between nucleus and electrons. The bigger the attraction, the smaller the atomic radius. Factors affecting the attraction of this is the number of protons in the nucleus and the amount of skin that contains the electrons.
Core with a lot of larger numbers of protons have a greater attraction for electrons, including the outermost electron. So, in a period from left to right, the radius of the smaller atoms. When we move from top to bottom in a class of periodic structure, the number of electron shells increases and, therefore, atomic radius increases as well.

2. Ionization Energy
Ionization energy is the minimum energy required to remove one electron from a neutral atom or an ion in the form of gas. Factors influencing the ionization energy, among others, the core charge, the distance from the core electrons, and the number of electrons that is between the outer and core electrons. In one group, atomic radius increases so that the core appeal of the smaller outer electrons, electrons are easily removed, the energy needed to remove more small. From left to right in one period, as described in the previous section, the core attraction of the greater electron, electrons are more difficult to be released, the greater ionization energy. It can be seen in this picture.












3. Electron Affinity
Electron affinity is the energy that accompanies the process of adding one electron on sati in the form of neutral gas atoms to form negative ions.










4. Electronegativity
Electronegativity is a number that states the tendency of an element to attract electrons in a chemical bond side. An atom's electronegativity is its atomic Affected by both weight and the distance That its valence electrons from the charged nucleus reside. The higher the electronegativity associated number, the more the element or compound Towards it attracts electrons.

periodic system: the brief summary

Periodic system shows grouping elements. Attempts to classify the elements has been started since the experts (in the late 18th century) found more and more elements. The simplest grouping is to divide the elements into metals and nonmetals.

In 1829, Johan Wolfgang Dobereiner see any similarities between the nature of some elements, and classify the elements of nature according to similarity. Each group was composed of three elements, so-called Triade. If the elements in one Triade increase ordered by atomic mass, atomic mass and it attributes the second element is the average of the atomic mass / properties first and third elements. Dobereiner findings showed a relationship between atomic mass and properties of elements.

In 1864 a British chemist named AR Newlands announced the discovery of the so-called law of octaves. Newlands arrange the elements according to their relative atomic mass increases. Proved the elements that differ 1 octave (element number 1 to number 8, element number 2 to number 9, and so on) show similarity properties. At Newlands octave compiled list, the elements of noble gases (He, Ne, Ar and so on) has not been found. Newlands octave law only applies to light elements (low Ar)

In 1869 the Russian scholar named Dmitri Ivanovich Mendeleev, based on observations of 63 elements known at that time, concluded that the properties of elements are periodic function of the relative atomic mass. That is, if the elements arranged according to their relative atomic mass increases, the specific properties will be repeated periodically. Mendeleev create the periodic elements of a list drawn up according to their relative atomic mass increases. Elements that have characteristics in common are placed in vertical columns called groups. Mendeleev periodic list published in 1872. There are several weaknesses in the Mendeleev periodic system: first, the placement of some elements not to increase their relative atomic mass. For example, the placement of tellurium (Te) and iodine (I). Heavier tellurium (Ar = 128) preceding the lighter iodine (Ar = 127). This upside-down placement had made considering the similarity in the nature groups elements. Iodine more shows similarities with the nature of fluorine, chlorine and bromine, while tellurium more shows similarities with the nature of oxygen, sulfur and selenium.
second, there are still many unknown elements at the time, so in the table there are many empty places.

In 1914 Henry GJ Moseley discovered that the order of elements in the periodic table according to the increase in atomic number elements. Placement of tellurium and iodine are not in accordance with the relative atomic mass increases, the increase was in accordance with the atomic number. Tellurium has atomic number 52 while the 53 iodine. A periodic nature rather as a function of atomic number.

Modern periodic system, which is also called long-form periodic system, arranged according to the increase in atomic number and similarity of properties. Modern periodic system can be considered as improvements Mendeleev periodic system.