NEWLANDS’ LAW OF OCTAVES

NEWLANDS’ LAW OF OCTAVES

Newland

  • In 1864, Newlands arranged the then-known elements in the order of increasing atomic masses and found that the properties of every eighth element are similar to the properties of the first element
  • Till then 56 elements were known.
  • Law of Octaves says that “If elements are arranged by the increasing order of their atomic masses, property of every eighth element (starting from the first element) repeats”
example of newland's octave law
example of Newland’s octave law

Limitation

  • It was found that the Law of Octaves was applicable only up to calcium, as after calcium every eighth element did not possess properties similar to that of the first.
  •  It was assumed by Newlands that only 56 elements existed in nature and no more elements would be discovered in the future.
  • But, later on, several new elements were discovered, whose properties did not fit into the Law of Octaves.
  •  In order to fit elements into his Table, Newlands adjusted two elements in the same slot, but also put some unlike elements under the same note.
  • Note that cobalt and nickel are in the same slot and these are placed in the same column as fluorine, chlorine, and bromine which have very different properties than these elements.
  • Iron, which resembles cobalt and nickel in properties, has been placed far away from these elements.
  • Thus, Newlands’ Law of Octaves worked well with lighter elements only.

Important Questions from Newlands’ Law of Octaves and Döbereiner’s Triads

  1. In Mendeleev’s periodic table, gap was not left for one of the following elements. This element is :
    (a) gallium (b) beryllium (c) germanium (d) scandium
  2. . The Newlands’ law of octaves for the classification of elements was found to be applicable only up to the element :
    (a) potassium (b) calcium (c) cobalt (d) phosphorus
  3.  According to Mendeleev’s periodic law, the elements were arranged in the periodic table in the order of :
    (a) decreasing atomic numbers (b) increasing atomic numbers (c) decreasing atomic masses (d) increasing atomic massesAns. b,b,d
  4. A part of the early classification of elements has been given below :
    H Li Be B C N O
    F Na Mg Al Si P S
    (
    a) Which law of classification of elements is illustrated by the above arrangement of elements?
    (
    b) Name the scientist who proposed such a classification of elements.
    (
    c) Why is such a classification of elements compared with a characteristic of musical scale?
    (
    d) State one limitation of this classification of elements.
    Ans

(a) Newlands’ law of octaves
(
b) Newlands
(
c) Because in this classification  the repetition in the properties of elements is just like the repetition of eighth note in an octave of music
(
d) This could be applied only up to the element calcium and not beyond that.

Q.5. Did Dobereiner’s triads also exist in the columns of Newlands’ octaves? Compare and find out.

  • Ans. Yes, Dobereiner’s triads also exist in the columns of Newlands’ classification of elements based on the law of octaves.
  • Consider the elements lithium (Li), sodium (Na), and potassium (K) which are present in the second column of Newlands’ classification of elements.
  • Now, if we start with lithium as the 1st element, then the 8th element from it is sodium, and according to Newlands’ law of octaves, the properties of 8th element sodium should be similar to those of the first element lithium.
  • Again, if we take sodium as the 1st element, then the 8th element from it is potassium, and according to Newlands’ law of octaves, the properties of 8th element potassium should be similar to those of the 1st element sodium.
  • This means that according to Newlands’ law of octaves, the elements lithium, sodium and potassium should have similar chemical properties.
  • We also know that lithium, sodium and potassium form a Dobereiner’s triad having similar.
  • we conclude that Dobereiner’s triads also exist in the columns of Newlands’ octaves.

Q.6. What were the limitations of Dobereiner’s classification of elements?

Ans. The main limitation of Dobereiner’s classification of elements was that it failed to arrange all the then-known elements in the form of triads of elements having similar chemical properties. Dobereiner could identify only three triads from the elements known at that time. So, his classification of elements was not much successful. Another limitation was that Dobereiner failed to explain the relation between atomic masses of elements and their chemical properties.
Q.7. What were the limitations of Newlands’ law of octaves?
Ans. Newlands’ law of octaves for the classification of elements had the following limitations :
(i) Newlands’ law of octaves was applicable to the classification of elements up to calcium only. After
calcium, every eighth element did not possess properties similar to that of the first element. Thus,
Newlands’ law of octaves worked well with lighter elements only.
(ii) Newlands assumed that only 56 elements existed in nature and no more elements would be discovered in the future. But later on, several new elements were discovered whose properties did not fit into Newlands’ law of octaves.
(iii) In order to fit elements into his table, Newlands put even two elements together in one slot and that too in the column of unlike elements having very different properties. For example, the two elements cobalt (Co) and nickel (Ni) were put together in just one slot, and that too in the column of elements like fluorine, chlorine, and bromine which have very different properties from these elements.

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