There were 63 known elements that Mendeleev included in his periodic table excluding eka-Boron,eka-aluminium,eka-silicon. Hence, total number of elements should be 63 but in NCERT total number of elements is 63 even after including scandium (eka-Boron), aluminum (eka-aluminium), silicon (eka-silicon),how is it possible?
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Elements are arranged in the periodic table in the increasing order of their relative atomic masses.
Mendeleev divided his periodic table in eight groups and seven periods.
Groups from I to VII are meant for normal elements and group VIII is for transition elements.
Groups from I to VII have been divided in two sub groups, while group VIII is meant for three elements.
Periods from 4th to 7th have been divided in two series: 1st series and 2nd series.
Elements having similar properties have been kept in the same group. For example; lithium, potassium, rubidium, etc. are in 1st group.
Two general formulae; one for oxides and second for hydrides; have been given for the elements of each group in the periodic table. For example: R2O for oxides and RH for hydrides, of the elements; of 1st group.
Using the given general formulae; the formula of oxides and hydrides can be written for the elements of each group. For example; hydrogen, sodium, potassium, etc. belong to the first group. The general formula of oxides for the elements of 1st group is R2O. Accordingly they form H2O, Na2O, K2O, etc.
Mendeleev divided his periodic table in eight groups and seven periods.
Groups from I to VII are meant for normal elements and group VIII is for transition elements.
Groups from I to VII have been divided in two sub groups, while group VIII is meant for three elements.
Periods from 4th to 7th have been divided in two series: 1st series and 2nd series.
Elements having similar properties have been kept in the same group. For example; lithium, potassium, rubidium, etc. are in 1st group.
Two general formulae; one for oxides and second for hydrides; have been given for the elements of each group in the periodic table. For example: R2O for oxides and RH for hydrides, of the elements; of 1st group.
Using the given general formulae; the formula of oxides and hydrides can be written for the elements of each group. For example; hydrogen, sodium, potassium, etc. belong to the first group. The general formula of oxides for the elements of 1st group is R2O. Accordingly they form H2O, Na2O, K2O, etc.
ashutosh6557:
I know this and this wasn't the answer I was looking for anyways thanks for answering.
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those elements were not known at that time and were not discovered.mendeleev predicted the properties of the elements by referring the properties of other elements in his perioddic table
sorry Rajesh this wasn't the answer I was looking for.
what is the problem with this answer
Actually my question was there were 63 known elements when Mendeleev formed his table right?
but scandium gallium and germanium weren't known by then
so if we disclude these three elements and count rest of the elements in his table then it should be 63
but in NCERT book's table if we don't include these elements then Total no' of elements are 60 that's my question!
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