Question

good morning'
ami one is having proper notes of ch periodic classification​

Answer 1

Answer.

CBSE Class 10 Science Notes Chapter 5 Periodic Classification of Elements..

“The periodic table is a tabular method of displaying the elements in such a way, that the elements having similar properties occur in the same vertical column or group”.

Earlier attempts of the classification of elements: Dobereiner’s Triads, Newland’s law of octaves.

Dobereiner’s Triads: This classification is based on the atomic mass. According to this, when elements are arranged in order of increasing atomic masses, groups of three elements, having similar properties are obtained. The atomic mass of middle element of the triad being nearly equal to the average of the atomic masses of the other two elements.

For Example Li (6.9), Na (23), K (39).Limitation: It fails to arrange all the known elements in the form of triads, even having similar properties.

Newland’s Law of Octaves: According to this ‘when elements are placed in order of increasing atomic masses, the physical and chemical properties of every 8th element are a repetition of the properties of the first element.’

Form of Newland’s octaves is given in the following table:

Periodic Classification of Elements Class 10 Notes Science Chapter 5 1

Limitations

Law of octaves was applicable only upto calcium (only for lighter elements).

Newland adjusted two elements in the same slot (e.g. Co and Ni), having different properties. For example; Co and Ni with Fluorine, Chlorine, Bromine and Iodine.

According to Newland, only 56 elements existed in nature and no more elements would be discovered in future.

Present attempts for the classification of elements: Mendeleev’s Periodic Table, the Modern Periodic Table....