Dobereinerβs triads and Newlandβs law of octaves were early attempts at classifying elements into groups based on their properties. Since many new elements were discovered over the course of the 18th and 19th centuries, the broad classification of elements into metals and non-metals became inefficient. Several experiments were conducted in order to identify elements with similar properties and group them together.

It is important to note that the primitive methods of classifying elements, such as Newlandβs law of octaves and Dobereinerβs triads, laid the foundation for the development of the modern periodic table.
Table of Content
- What are Dobereiner’s Triads?
- Limitations of Dobereiner’s Triads
- Newland’s Law of Octaves
- Limitations of Newland’s Law of Octaves
- Frequently Asked Questions – FAQs
What are Dobereinerβs Triads?
Dobereinerβs triads were groups of elements with similar properties that were identified by the German chemist Johann Wolfgang Dobereiner. He observed that groups of three elements (triads) could be formed in which all the elements shared similar physical and chemical properties.
Dobereiner stated in his law of triads that the arithmetic mean of the atomic masses of the first and third element in a triad would be approximately equal to the atomic mass of the second element in that triad. He also suggested that this law could be extended for other quantifiable properties of elements, such as density.
The first of Dobereinerβs triads was identified in the year 1817 and was constituted by the alkaline earth metals calcium, strontium and barium. Three more triads were identified by the year 1829. These triads are tabulated below.
Triad 1
This triad was made up of the alkali metals lithium, sodium and potassium.
Triad | Atomic Masses |
Lithium | 6.94 |
Sodium | 22.99 |
Potassium | 39.1 |
The arithmetic mean of the masses of potassium and lithium corresponds to 23.02, which is almost equal to the atomic mass of sodium.
Triad 2
As mentioned earlier, calcium, barium and strontium formed another one of Dobereinerβs triads.
Triad | Atomic Masses |
Calcium | 40.1 |
Strontium | 87.6 |
Barium | 137.3 |
The mean of the masses of barium and calcium corresponds to 88.7.
Triad 3
The halogens chlorine, bromine and iodine constituted one of the triads.
Triad | Atomic Masses |
Chlorine | 35.4 |
Bromine | 79.9 |
Iodine | 126.9 |
The mean value of the atomic masses of chlorine and iodine is 81.1.
Triad 4
The fourth triad was formed by the elements sulfur, selenium, and tellurium.
Triad | Atomic Masses |
Sulfur | 32.1 |
Selenium | 78.9 |
Tellurium | 127.6 |
The arithmetic mean of the masses of the first and third elements in this triad corresponds to 79.85.
Triad 5
Iron, cobalt and nickel constituted the last of Dobereinerβs triads.
Triad | Atomic Masses |
Iron | 55.8 |
Cobalt | 58.9 |
Nickel | 58.7 |
However, the mean of the atomic masses of iron and nickel corresponds to 57.3.
Limitations of Dobereinerβs Triads
The key shortcomings of Dobereinerβs method of classifying elements are listed below.
- The identification of new elements made this model obsolete.
- Newly discovered elements did not fit into the triads.
- Only a total of 5 Dobereinerβs triads were identified.
- Even several known elements did not fit into any of the triads.
Owing to these shortcomings, other methods of classifying elements were developed.
Newlandβs 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, Newlandβs 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 Newlandβs law of octaves is provided below.
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 Newlandβs Law of Octaves
The key shortcomings of Newlandβs law of octaves are listed below.
- Several elements were fit into the same slots in Newlandβs 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.
- Newlandβs 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 Newlandβs law of octaves and Dobereinerβs Triads along with other related concepts, such as Mendeleevβs periodic table, register with BYJUβS and download the mobile application on your smartphone.
Frequently Asked Questions on Newlandβs Law Of Octaves
What is the law of triads?
The law of triads states that the arithmetic mean of the atomic masses of the first and third elements in a triad would be approximately equal to the atomic mass of the second element in that triad.
What is the law of octave?
The law of octave states that every eighth element has similar properties when the elements are arranged in the increasing order of their atomic masses.
Why was Dobereinerβs triad discarded?
Dobereinerβs triad was discarded because it failed to arrange all the known elements in the form of triads.
Why was the Newlands law of octaves discarded?
Newlands law of octaves was discarded because it failed to arrange larger elements beyond Calcium.
What is the law of the modern periodic table?
The law of the modern periodic table states that the chemical properties of an element are a periodic function of its atomic number.
Superrr
good and helpful
Thanks, really helpful
Thank you for the help
Thank you It really helped in my exam that I have tomorrow! Thx Byjus for helping me out
Really great and helpful. Thankyou Byjus .
best and useful app best app in the world
.