Mendeleev Periodic Table - Meaning, Definition, Characteristics, Drawback, FAQs

Mendeleev Periodic Table - We all know that our periodic table contains 118 elements. Natural elements account for 94 of the 118 elements, whereas manufactured elements account for 24. Only 30 elements were known in the year 1800. Scientists were finding it difficult to remember the elements and their properties as more were discovered. They began collecting and classifying information on the elements. The tabular categorization of items based on their attributes became widespread. The periodic table is a tabular form structure in which various elements are grouped according to their properties.

Introduction to Mendeleev Periodic Table

The most important contributor to the early construction of the periodic table was Russian scientist Dmitri Ivanovich Mendeleev. Many periodic tables have been created, but the Mendeleev periodic table is the most important.

The Mendeleev Periodic Table was introduced in 1869, following the rejection of Newlands Octave Law. Elements were arranged in Mendeleev's periodic chart according to their fundamental property, atomic mass, and chemical characteristics. Only 63 elements were known at Mendeleev's time. Mendeleev discovered that the properties of elements were related to atomic mass in a periodic pattern after analysing their qualities. He ordered the elements in the periodic table so that those with comparable properties were in the same vertical columns.

Mendeleev created a row of elements in ascending atomic weight order. He halted that row and started a new one below it as soon as the attributes of the elements were determined to be repeated. The element that displayed the properties' repetition was placed in the first slot of this new row.

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What is Mendeleev Periodic Law?

“The Physical and Chemical Properties of the Elements are Periodic Functions of Their Atomic Weights,” Mendeleev's law asserts.

What was Mendeleev's Method for Arranging Elements?

Mendeleev first organised elements in order of increasing atomic weight, one below the other. Elements with comparable characteristics are grouped together. In the same horizontal row, you'll find elements with identical attributes. The following is Mendeleev's initial periodic table, which was published in 1869.

Reversing the order of the elements in Mendeleev's periodic table helps you understand it better.

• The elements are arranged in a horizontal line in ascending order of atomic mass.

• A ‘period' is a horizontal arrangement of elements.

• When an element has a high degree of similarity to an earlier element, the new element is inserted just beneath the earlier element with comparable properties to begin a new period.

• A ‘column' is formed by the periods stacked one on top of the other (group). Mendeleev's periodic table, then, is made up of horizontal rows and vertical columns, or periods and groups.

• If the elements are similar but not identical, they are put below but somewhat distant from each other to differentiate them. Each column will be divided into two sub-columns (A and B), with components from the same sub-columns sharing greater similarities.

Characteristics of Mendeleev Periodic Table

• In Mendeleev's periodic table, vertical columns and horizontal rows were classified as groups and periods, respectively.

• The periodic table is divided into seven horizontal rows, or periods, with numbers ranging from 1 to 7.

• The attributes of components in the horizontal rows (periods) have a predictable gradient from left to right.

• Eight vertical columns or groups make up the periodic table. They are numbered from one to eight.

• To distinguish between elements that are similar but not identical, it is positioned below and slightly away from the other. As a result, each column will have two sub-columns A and B, allowing components in the same sub-columns to be more comparable.

• Normal elements belong to groups I through VII, while transition elements belong to group VIII.

• Groups I through VII are separated into two subgroups, with Group VIII including three elements.

• The 4th through 7th grades are separated into two series: 1st series and 2nd series.

• Elements with comparable characteristics have been grouped together. Lithium, potassium, rubidium, and other elements in the first group are examples.

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Merits of Mendeleev Periodic Table

1. In the arrangement, similarity in properties were given greater priority than atomic mass.

Iodine, despite having a lower mass (127) than Tellurium (128), is placed later because it resembles chlorine and bromine more than oxygen and sulphur. Similarly, increasing atomic mass has little effect on cobalt and nickel.

2. Atomic mass correction

Elements of beryllium, indium, gold, and platinum were projected to have wrong mass based on periodic properties, leading to a re-estimation of their true mass.

3. Prediction of new elements

It was able to predict the existence and properties of three elements with properties that were comparable to boron, aluminium, and silicon. Eka-boron, Eka-aluminum, and Eka-silicon were the names of these elements. They were isolated and given the names scandium, gallium, and germanium.

Their oxides and halides had experimentally determined atomic weights, physical qualities, and chemical formulas that were identical to those anticipated by Mendeleev. The incomplete periods suggest the existence of elements that had yet to be discovered.

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Demerits or Drawbacks of Mendeleev Periodic Table

• Because it contains qualities of both alkali metals and halogens, Mendeleev's table was unable to assign a valid position to Hydrogen. Hydrogen, like alkali metals, can form compounds with halogens, oxygen, and sulphur. Hydrogen, like the halogens, possesses diatomic molecules and forms covalent compounds with metals and non-metals.

• Because one of the criteria in Mendeleev's table is atomic mass, isotopes of the same element must be placed in a different slot. This can lead to a major mistake.

• The atomic masses of the elements do not rise in a consistent fashion, as can be seen in the table. As a result, it is impossible to say how many elements will be discovered with atomic masses that fall between two existing atomic masses.

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