Definition Of Mendeleev?s Periodic Table

Definition Of Mendeleev?s Periodic Table

In 18690 Russian chemist Dmitri Mendeleev Published a Periodic Table and corresponding periodic law of 63 elements known at that time

Mendeleev’s Periodic Law states that “The Physical and Chemical Properties of the elements are periodic functions of their atomic weights.”

• Mendeleev created a periodic table by listing elements in a row in order of atomic weight and starting a new row the characteristics of element began to repeat
• This resulted in arrangement where the element with similar properties occupies the same vertical column
• Mendeleev called these vertical columns as Groups and resultant horizontal rows as Series
• Mendeleev success roots to his vision of classification of elements based on similarities in their empirical formulas and properties of compounds formed by them
• This made him to occasionally ignore the order suggested by atomic weights to classify elements with similar properties together
• For example Iodine with lower atomic weight than Tellurium was placed in Group 7 along with fluorine, chlorine and iodine because of its similarities with their properties
• Mendeleev also left gaps in his periodic table for undiscovered elements
• For example he left gap under aluminum, silicon and Boron in the periodic table for yet to be discovered elements
• Mendeleev not only predicted the existence of these elements and called them Eka-Aluminium, Eka-silicon and Eka-Boron respectively
• Mendeleev also described some of the general physical properties of above elements
• Later these elements discovered and named as Gallium, Germanium and Scandium
• However Mendeleev’s periodic table has certain drawbacks
• Drawbacks of Mendeleev’s Periodic Table:
• - a. Position of element hydrogen is not clear
- b. There is no place for isotopes of elements in his periodic table
- c. The placement of element having greater atomic mass before the elements having lower atomic mass could not be logically explained

Solved Example:

Ques: 1. Mendeleev called horizontal rows in periodic table as ____

A. Periods
B. Groups
C. Series
D. Points