As a large number of elements were discovered it was realized that it was not possible to chew over all the elements and their compounds by a chemist unless they are classified. Following are the reasons for the classification of elements.
early chemists realized that there are two kinds of elements,i e.,metals and non-metals which can be distinguished from each other o the basis of a set of physical and chemical properties.
Chemically similar elements arranged in the order of their atomic weights in the groups of three elements constitutea triad such that at wt of lay element of a triad is almost the arithmetic convey of the at wt of other two elements.
The most significant achievement of the triads classification is that it recognised for the first time the relation between at wt of an element and the properties of an element.
In 1863. Newland arranged the elements known at that measure in the increasing request of their at wts. He found that elements with similar properties recurred each time afterevery seven elements much the same way as the same way as the repetition of musical notes in an octave. This regularity by repitition was termed by him as law of octaves.
Elements when arranged in the increasing request of their at wts show resemblance in physical and chemical properties between the eighth and first element similar to the eighth and first note of musical measure.
Periodic delay is a chart of elements prepared in such a way that elements having similar physical and chemical properties occur in the same vertical column commonly called assort.
The word periodic is used because elements having similar physical and chemical properties are repeated after certain interval or period. This is called periodicity of properties of the elements.
By the year 1869. Dmriti Invanovich Mendeleev studied the physical and chemical properties of all the 63 elements known at that measure. He arranged these elements in the form of a delay on the following basis:
A tabular chart representing systematic arrangement of elements in groups and periods in the order of their increasing atomic weights is called Mendeleev's periodic table.
1. There are eight vertiacl columns called groups. The groups from I to VII are sub-divided into two sub-groups a and b. Thus there are 15 vertical columns or groups in all.
2. Some gaps were left knowingly by Mendeleev for undiscovered elements. This accelerated the process of discovering these elements as their properties were predicted by Mendeleev on the basis of other elements show in the same group.
As a large number of elements were discovered it was realized that it was not possible to study all the elements and their compounds by a chemist unless they are classified. Following are the reasons for the classification of elements.
early chemists realized that there are two kinds of elements,i e.,metals and non-metals which can be distinguished from each other o the basis of a set of physical and chemical properties.
Chemically similar elements arranged in the request of their atomic weights in the groups of three elements constitutea triad such that at wt of middle element of a triad is almost the arithmetic mean of the at wt of other two elements.
The most significant achievement of the triads classification is that it recognised for the first measure the relation between at wt of an element and the properties of an element.
In 1863. Newland arranged the elements known at that time in the increasing request of their at wts. He found that elements with similar properties recurred each time afterevery seven elements much the same way as the same way as the repetition of musical notes in an octave. This regularity by repitition was termed by him as law of octaves.
Elements when arranged in the increasing order of their at wts show resemblance in physical and chemical properties between the eighth and first element similar to the eighth and first say of musical measure.
Periodic delay is a chart of elements prepared in such a way that elements having similar physical and chemical properties occur in the same vertical column commonly called group.
The evince periodic is used because elements having similar physical and chemical properties are repeated after certain interval or period. This is called periodicity of properties of the elements.
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