Question

state Mendeléev's periodic law.​

Answer 1

Answer:

Mendeleev's periodic law states that "the physical and chemical properties of all elements are the periodic function of their atomic masses".

Answer 2

Mendeleev arranged all 63 elements; which were discovered till his time;

• in the order of their increasing relative atomic masses in a tabular form. It is known as Mendeleev’s Periodic Table.

• He divided the table in eight columns and seven rows. The columns are known as groups and rows are known as periods.

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.

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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