What breakthrough did Mendeleev make in devising a periodic table that was accepted by the scientific community?He devised the ‘law of octaves’He published the first full list of all the elementsHe left gaps in the table for unknown elementsHe arranged the elements in order of atomic weight

Dmitri Mendeleev made several key breakthroughs in devising a periodic table that was accepted by the scientific community.

1. Arrangement of Elements: Mendeleev arranged the elements in order of increasing atomic weight. This was a significant step as it allowed for the classification of elements based on their atomic weight.

2. Prediction of Unknown Elements: Perhaps the most revolutionary aspect of Mendeleev's periodic table was that he left gaps for elements that were not yet discovered. He even predicted the properties of these unknown elements based on their position in the table. This was a bold move that was later validated with the discovery of these elements, which fit perfectly into the gaps he had left. This greatly increased the acceptance of his periodic table in the scientific community.

3. Publication of Elements: Mendeleev also published the first full list of all the known elements at the time. This was a significant contribution as it provided a comprehensive reference for scientists.

However, it's important to note that it was not Mendeleev who devised the 'law of octaves'. This was proposed by John Newlands, another scientist working on the classification of elements. Newlands noticed that every eighth element had similar properties, hence the name 'law of octaves'.