Who made the first attempt to classify elements systematically?

Question: Who made the first attempt to classify elements systematically?

The first attempt to classify elements systematically was made by **Johann Wolfgang Döbereiner**, a German chemist, in the early 19th century. He grouped elements with similar properties into triads, such as lithium, sodium and potassium. He observed that the atomic weight of the middle element was approximately the average of the other two elements in the triad . However, this method was not applicable to all elements and had many limitations.

Later, in 1863, **John Alexander Reina Newlands**, an English chemist, proposed the Law of Octaves. He arranged the elements in ascending order of their atomic weights and noticed that every eighth element had similar properties, like the notes of music . However, this law was also flawed and could not accommodate more than 56 elements.

The most successful attempt to classify elements systematically was made by **Dmitri Ivanovich Mendeleev**, a Russian chemist, in 1869. He arranged the elements in increasing order of their atomic weights and also according to their chemical properties. He left gaps for undiscovered elements and predicted their properties based on the periodic trends. His periodic table was later modified by Henry Moseley, who used atomic numbers instead of atomic weights as the basis of classification.