"preiodic classification" chap explained
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In this chapter the classification of elements on the basis of their properties is explained.
First of all in year 1817 Döbereiner,a german chemist tried to arrange the elements on the basis of their chemical properties.
Döbereiner's law of triad:-
according to Döbereiner's law of triad:
-when elements are arranged in the increasing order of their atomic masses then groups of three elements (known as triad) having similar chemical properties are obtained.
Limitations:-
• he could find only three triads from the known elements of that time.
Newlands' law of octaves:-
In 1866 an English chemist has founded that whe elements are arranged in the increasing order of their atomic masses the every 8th element(starting from a given one)have properties similar to that of 1st element.
Limitations:-
• His law worked properly up to the calcium only.
• He assumed that no only 56 elements exist in nature and no other elements will be discovered in future.
• His law worked to the lighter elements only.
• He had placed unlike elements in the same note but also placed two elements in the same slot.
Mendeleev's periodic table:-
When Mendeleev started his work,only 63 elements were known.He examined the relatipnship b/w their physical and chemical properties.Among chemical properties Mendeleev concentrated on the oxides and hydrides formed by the elements.
Limitations:-
He had placed gaps for the future elements.
In order to place the elements of the similar chemical properties he had disturbed the order of the increasing atomic masses of the elements.
Modern periodic law:-
In th modern periodic law elements were arranged in the increasing order of their atomic number. It removed limitations that were faced by the scientists when they arranged the elements in their increasing atomic mass.
Modern periodic table:-
• 7 periods(horizontal rows)
• 18 groups(vertical columns)
• noble gases were placed in 18th group.
First of all in year 1817 Döbereiner,a german chemist tried to arrange the elements on the basis of their chemical properties.
Döbereiner's law of triad:-
according to Döbereiner's law of triad:
-when elements are arranged in the increasing order of their atomic masses then groups of three elements (known as triad) having similar chemical properties are obtained.
Limitations:-
• he could find only three triads from the known elements of that time.
Newlands' law of octaves:-
In 1866 an English chemist has founded that whe elements are arranged in the increasing order of their atomic masses the every 8th element(starting from a given one)have properties similar to that of 1st element.
Limitations:-
• His law worked properly up to the calcium only.
• He assumed that no only 56 elements exist in nature and no other elements will be discovered in future.
• His law worked to the lighter elements only.
• He had placed unlike elements in the same note but also placed two elements in the same slot.
Mendeleev's periodic table:-
When Mendeleev started his work,only 63 elements were known.He examined the relatipnship b/w their physical and chemical properties.Among chemical properties Mendeleev concentrated on the oxides and hydrides formed by the elements.
Limitations:-
He had placed gaps for the future elements.
In order to place the elements of the similar chemical properties he had disturbed the order of the increasing atomic masses of the elements.
Modern periodic law:-
In th modern periodic law elements were arranged in the increasing order of their atomic number. It removed limitations that were faced by the scientists when they arranged the elements in their increasing atomic mass.
Modern periodic table:-
• 7 periods(horizontal rows)
• 18 groups(vertical columns)
• noble gases were placed in 18th group.
PrajjwalSingh:
thanks shishira for marking as branliest answer
ok wc
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