what was the basis of classification of elements by newland?plz explain
Answers
Answer:
Newland’s Law of Octaves
In the year 1864, the British chemist John Newlands attempted the 62 elements known at that time. He arranged them in an ascending order based on their atomic masses and observed that every 8th element had similar properties. On the basis of this observation, Newland’s law of octaves was formulated.
The law of octaves states that every eighth element has similar properties when the elements are arranged in the increasing order of their atomic masses. An illustration detailing the elements holding similar properties as per Newland’s law of octaves is provided below.
Newland's Law of Octaves
Newlands compared the similarity between the elements to the octaves of music, where every eighth note is comparable to the first. This was the first attempt at assigning an atomic number to each element. However, this method of classifying elements was met with a lot of resistance in the scientific community.
Limitations of Newland’s Law of Octaves
The key shortcomings of Newland’s law of octaves are listed below.
Several elements were fit into the same slots in Newland’s periodic classification. For example, cobalt and nickel were placed in the same slot.
Elements with dissimilar properties were grouped together. For example, the halogens were grouped with some metals such as cobalt, nickel, and platinum.
Newland’s law of octaves held true only for elements up to calcium. Elements with greater atomic masses could not be accommodated into octaves.
The elements that were discovered later could not be fit into the octave pattern. Therefore, this method of classifying elements did not leave any room for the discovery of new elements.
To learn more about Newland’s law of octaves and Dobereiner’s Triads along with other related concepts.
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Explanation:
John Alexander Newlands' Law of Octaves
An English chemist John Alexander Reina Newlands in 1864 noted that every eighth element showed similar physical and chemical properties, when the elements are placed in the increasing order of their atomic masses. This was called as the Newlands' law of octaves.
The law states that when elements are placed in the increasing order of atomic masses, the properties of the eight element are repeated.
Newlands arranged the elements then known in the following manner.
Li Be B C N O F
Na Mg Al Si P S Cl
K Ca
Row of elements had seven elements and the eighth fell under the first element.
In those days, the number of elements known were very limited and no elements from the noble or inert gas elements such as helium (He), neon (Ne), argon (Ar), etc. were known.
For example, if we take beryllium (Be) as the first element, the eighth element from Be is magnesium (Mg). If we continue in the similar fashion, the eighth element after Mg is calcium Ca. According to Newlands' law, the elements Be, Mg and Ca should display similar chemical and physical properties. They do. The elements Be, Mg, Ca fall under the group of alkali-earth metals. All these elements are metallic in nature, their oxides are alkaline in nature and they have a valence of +2.