The modern periodic table is based on the periodic law proposed by:
A. Henry Moseley
B. Dmitri Mendeleev
C. Niels Bohr
D. John Dalton
Answer: Option A
Solution (By JKSSB Mock Tests)
Henry Moseley discovered that the atomic number (number of protons) is the fundamental property of an element, not atomic mass. He proposed the modern periodic law: properties are periodic functions of atomic numbers. Mendeleev's law was based on atomic mass, which had anomalies.
Explanation:
To name this alkane, find the longest continuous carbon chain, which has 4 carbons (butane). Number the chain from the end closest to the substituent to give it the lowest possible number. The methyl group is on the second carbon. Thus, the IUPAC name is 2-methylbutane. Isopentane is its common name.
Explanation:
Bakelite (phenol-formaldehyde) is thermosetting; once set, it cannot be remolded. Polyethylene, PVC, and nylon are thermoplastics – they soften on heating.
Explanation:
In the sulfate ion (SO4 2-), the central sulfur atom is bonded to four oxygen atoms with no lone pairs on the sulfur. The steric number is 4 (4 sigma bonds + 0 lone pairs). A steric number of 4 corresponds to sp3 hybridization, resulting in a tetrahedral geometry.
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