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What are the salient features of Mendeleév's periodic table?
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Explanation of Mendeleev’s Periodic Table:
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.
Merits of Mendeleev’s Periodic Table:
Mendeleev left some blank spaces in his periodic table in order to place the elements having similar properties in the same group.
For example; titanium has been placed in IVth group, leaving a blank space adjacent to it in IIIrd group. Similarly, arsenic has been placed in Vth group; leaving two adjacent spaces blank.
These spaces have been occupied by scandium, gallium and germanium after their subsequent discovery.
Prediction for the elements to be discovered in future:
Mendeleev predicted the discovery of some elements and named them as eka-boron, eka-aluminium and eka-silicon. He gave the name of these elements prefixing the word ‘eka’ to the name of the preceding elements.
Scandium, Gallium and Germanium have been discovered later and took the place of eka-carbon, eka-aluminium and eka-silicon, respectively in the gap left in the Mendeleev’s Periodic table; as their properties were exactly similar to the predicted elements.
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.
Merits of Mendeleev’s Periodic Table:
Mendeleev left some blank spaces in his periodic table in order to place the elements having similar properties in the same group.
For example; titanium has been placed in IVth group, leaving a blank space adjacent to it in IIIrd group. Similarly, arsenic has been placed in Vth group; leaving two adjacent spaces blank.
These spaces have been occupied by scandium, gallium and germanium after their subsequent discovery.
Prediction for the elements to be discovered in future:
Mendeleev predicted the discovery of some elements and named them as eka-boron, eka-aluminium and eka-silicon. He gave the name of these elements prefixing the word ‘eka’ to the name of the preceding elements.
Scandium, Gallium and Germanium have been discovered later and took the place of eka-carbon, eka-aluminium and eka-silicon, respectively in the gap left in the Mendeleev’s Periodic table; as their properties were exactly similar to the predicted elements.
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