Identify the TRUE statements from the following
a) John Newlands arranged the known elements in the order of increasing atomic masses.
b) He started with the element having the lowest atomic mass (hydrogen) and ended at thorium which was the 56th element.
c) He found that every eighth element had properties similar to that of the first.
d) He compared this to the octaves found in music. Therefore, he called it the ‘Law of Octaves’
The question asks to identify the true statements regarding John Newlands' Law of Octaves. We need to evaluate each statement (a, b, c, d) based on the historical development of the periodic table.
John Newlands was one of the first scientists to attempt to classify elements. He indeed arranged the then-known elements in the order of their increasing atomic masses. This statement is TRUE.
Newlands started his arrangement with hydrogen, the element with the lowest atomic mass. His classification was applicable only up to calcium. However, he did arrange elements up to thorium, which was the 56th element known at that time. This statement is TRUE.
Newlands observed a repeating pattern in the properties of elements. He noticed that the properties of the eighth element were similar to those of the first element when arranged in increasing order of atomic mass. For example, lithium (Li) and sodium (Na) have similar properties, and sodium is the eighth element after lithium. This statement is TRUE.
Because of the repeating pattern of properties every eighth element, similar to the musical octaves where every eighth note is similar to the first, Newlands named his classification the 'Law of Octaves'. This statement is TRUE.
Correct Option: C) All a,b,c,d
The question asks about Newlands' Law of Octaves, a historical attempt to classify elements. We need to identify which pair of elements, according to Newlands' arrangement, exhibited similar properties.
Correct Option: B) Lithium and Sodium — According to Newlands' Law of Octaves, when elements were arranged in increasing order of their atomic masses, the properties of every eighth element were found to be similar to the first. Lithium and Sodium fall into this pattern, with Sodium being the eighth element after Lithium, and both exhibiting similar chemical properties (e.g., highly reactive metals).
The question asks about the limitation of Newlands' Law of Octaves. This law stated that when elements are arranged in increasing order of their atomic masses, the properties of every eighth element are similar to the first. We need to identify the element up to which this law was found to be applicable.
A) Calcium. Newlands' Law of Octaves was applicable only up to Calcium. After Calcium, every eighth element did not possess properties similar to that of the first, making the law invalid for heavier elements.
The question asks about the number of elements known to John Newlands when he proposed his Law of Octaves. This requires recalling a specific historical detail about the development of the periodic table.
Correct Option: D) When John Newlands proposed his Law of Octaves in 1865, there were 56 known elements in nature. He arranged these elements in increasing order of their atomic masses.
The question asks about the discovery that rendered the Law of Octaves irrelevant. This requires knowledge of the history of the periodic table and the limitations of early classification systems.
Correct Option: C) The discovery of Noble gases rendered the Law of Octaves irrelevant. Newlands' Law of Octaves was based on the assumption that there were no elements between the existing ones. The noble gases, being inert and having a full outer shell, did not fit into the existing octaves pattern, thus breaking the periodicity Newlands had proposed.
The question asks about the fundamental property used by Mendeléev to arrange elements in his Periodic Table. This requires recalling the basis of Mendeléev's classification.
Correct Option: A) Atomic mass was the fundamental property used by Mendeléev to arrange elements in his Periodic Table, along with the similarity of chemical properties.