This article gives an overview about the types of elements in the periodic table in addition to giving overview about their chemical behavior.
The periodic table is a convenient way to arrange the atoms in nature according to their chemical and physical properties.
Atoms in the periodic table are arranged according to their metallic characters and their nonmetallic properties. Atoms in the periodic table that are located in the left side of the table usually are considered to have metallic properties while those elements that are located in the right side of the periodic table have in general nonmetallic properties. As we go down the periodic table, the metallic properties of the elements increase.
Between the elements in the periodic table that show purely metallic character and which are located in the extreme left side of the periodic table and the nonmetal group of atoms that are located in the extreme right side of the periodic table there is the group of metals that is called the transition metals. This is a whole block of elements that contain many elements that are also metals in their chemical behavior but they differ than the typical metals of the alkali and alkaline earth metals by their use of 5-d orbitals in their bonding with ligands and organic functional groups.
These two groups of atoms are the lanthanides and the actinides groups of elements. These two groups of atoms possess metallic character that is similar to a characteristic metal. The difference is due to the presence in these atoms of new type of orbitals that can participate in the bonding of these metals with ligands and atoms. The use of additional 7 f-orbitals by these two groups of elements to make chemical bonds has mainly effect on the coordination number that these elements can make in their bonding which can reach a coordination number of 12 in some cases. This fact confers speciality to these atoms although the general metallic character in these two groups of atoms is conserved. This is manifested for example by their bonding with organic functional groups. The typical chemistry in this case is the nucleophilic character of the organic functional group that is attached to the lanthanide or the actinide atoms. This is a typical behavior that is observed in all metals o the periodic table including the transition metals.
Most elements in the periodic table possess metallic properties to varying degrees. The general chemical behavior of these atoms is to reach a state of minimum energy that is manifested as closed valence electronic shell that is full with electrons. This is a general trend of all metals and also of the nonmetallic group of atoms. The chemical difference between the two groups of atoms is by their mechanism to reach this state of electronic saturation at the valence electronic shell. Metals usually reach this state of electronic saturation by giving its extra electrons that are located in the outermost electronic shell. While in the nonmetallic group of atoms, the tendency to reach the state of closed electronic shell is achieved by getting extra electrons from outer sources. For these reasons metals are considered as good reducing agents while nonmetals are considered as good oxidizing agents.
The difference is not restricted to their chemical properties but is also extended to their physical properties, such as the boiling points and the state of the matter in each group of elements. Metals are usually solids at room temperature except for the element of mercury. Nonmetals can be present in any possible state of the matter. For example, the halogens are mainly existent in the gas phase at room temperature. An exception is the bromine molecule which is existent in the liquid phase at room temperature. The tendency of metals to give its outermost electrons to reach a state of minimum energy confers to these metals weak electronegative character. On the other hand, the tendency of the metals to accept extra electrons in order to reach a state of complete outermost electronic shell with electrons confers strong electronegative behavior to these atoms. This difference in electro-negativities between the two groups of atoms makes them behave completely differently in their manner of chemical bonding with other atoms.
Atoms with similar as well as with different values of electro-negativities can combine chemically to form chemical bonds. The type of bonding in each case is different. Atoms that have similar electro-negativities usually have chemical bonding that is of covalent nature. Atoms of varying degree of electro-negativities usually have chemical bonding of the ionic type.
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