The Periodic table represents a simple systematic way of classifying elements. A Russian Scientist Mendeleev 1869 formulated the periodic law based on the relative atomic mass of the elements however, the modern version which is currently in use today is based on their atomic numbers and it was suggested by Moseley in 1914.
Before we continue, it is important to state the periodic law. The law states thatt he physical and chemical properties of elements are periodic functions of their atomic numbers. The law can be restated as when elements are arranged in order of their increaing atomic numbers, their physical and chemical properties recur physically.
Basic Features Of The Periodic Table
The two basic features in the periodic table are groups and periods. The groups consist of elements in the same vertical column and generally, there are eight main groups with each group forming a family of elements represented by Roman numerals I, II, III, IV, V, VI, VII, and 0. Elements in the same group have the same number of valence electrons in their respective atoms that is, they have similar outermost shell electronic configurations.
Certain group elements have their family names with Group I elements known as alkali metals, Group II elements known as alkaline-earth metals, Group VII elements known as halogens, and Group 0 elements known as noble, inert, or rare- gases.
Elements in the same horizontal row are known as Periods and from the diagram above, you can see that the first twenty elements occupy the first four periods though this periodic table is not complete. Atoms of elements in the same period have the same number of shells of electrons with the highest occupied energy level in the electronic configuration of an element representing a period.
Block Of Elements In The Periodic Table
The first twenty elements in the periodic table are in blocks based on the types of their valence orbitals. There are three blocks for the first twenty elements namely s-block, p-block, and noble-block. The s-block elements have their valence electrons in the s orbitals except for helium while the p-block has the outermost electrons partially filled in the p-orbitals and elements in groups 3,4,5,6, and 7 are usually classified as p-block elements.
Noble elements are those in which the highest occupied energy levels are completely filled with electrons and they belong to group 0.
Relationship Among Elements[Group & Periods]
There is a relationship that exists among elements in the same group and period and we would outline some of them here. Elements in the same group have the same number of valence electrons and such groups of elements show similarities in chemical properties because of this factor. Going from left to right across a period, the metallic character decreases as there is a gradual change from metals in group IV to non-metals in groups V, VI, and VII, and finally to noble gases.
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