The question asks to identify the scientist who proposed the 'Law of Octaves' for classifying elements. This requires knowledge of the historical development of the periodic table and the contributions of various scientists.
C) John Newlands
John Newlands, an English chemist, proposed the 'Law of Octaves' in 1865. He arranged the then-known elements in order of increasing atomic weights and observed that every eighth element exhibited similar properties, akin to the notes in a musical octave. For example, the properties of lithium (Li) were similar to sodium (Na), which was the eighth element after lithium in his arrangement.
The question asks about the basis of the Modern Periodic Law. This law is a fundamental principle in chemistry that describes how the properties of elements repeat periodically. Understanding the historical development of the periodic table, from Mendeleev's initial classification to the modern version, is key to answering this question.
D) Atomic number — The Modern Periodic Law is based on the atomic number because it represents the number of protons in an atom, which determines the element's identity and its electronic configuration. The electronic configuration, in turn, dictates the chemical properties of an element, leading to periodic trends.
The question asks about the number of periods in the Modern Periodic Table. To answer this, one needs to recall the structure and organization of the periodic table, specifically the horizontal rows.
B) The Modern Periodic Table has 7 periods. Each period corresponds to the principal energy level of the outermost electrons in an atom.
The question asks about the number of groups in the Modern Periodic Table. This is a fundamental concept in chemistry, directly related to the organization and properties of elements. We need to recall the structure of the Modern Periodic Table to identify the correct number of groups.
Correct Option: C) 18 is the correct number of groups in the Modern Periodic Table, as per the IUPAC standard.
The question asks to identify the period in the periodic table that is considered the longest, containing 32 elements. This requires knowledge of the structure of the periodic table and the number of elements in each period.
B) Period 6 — Period 6 contains 32 elements: 2 s-block elements, 10 d-block elements, 6 p-block elements, and 14 f-block elements (Lanthanides). This makes it one of the two longest periods in the periodic table, and often referred to as the longest complete period.
The question asks to identify the block in the periodic table where transition elements are located. This requires knowledge of the classification of elements into different blocks (s, p, d, f) based on their electronic configuration.
Correct Option: C) d-block. Transition elements are defined by the filling of their d-orbitals and are thus located in the d-block of the periodic table.