​The Law of Octaves' was proposed by: ​

Correct option is A

The correct answer is (a) Alexander Newlands.

• The Law of Octaves was proposed by John Alexander Newlands, an English chemist, in 1864.
• According to this law, when elements are arranged in increasing order of their atomic masses, every eighth element exhibits similar chemical properties, much like the octaves in music.

Information about the Other Options:

• Dmitri Mendeleev: Known for the Periodic Table (1869), which arranged elements based on atomic masses and predicted the discovery of new elements.
• Lothar Meyer: Developed a periodic table around the same time as Mendeleev but was not associated with the Law of Octaves.
• Johann Dobereiner: Proposed the concept of Dobereiner's Triads, grouping elements with similar properties into sets of three.

Information Booster:

• The Law of Octaves was a precursor to the modern Periodic Law, which is based on atomic numbers rather than atomic masses.