Who developed the modern periodic table based on atomic numbers?
A. John Newlands
B. Henry Moseley
C. Dmitri Mendeleev
D. Lothar Meyer
Answer: Option B
Solution (By JKExamLibrary)
Henry Moseley established that the properties of elements are periodic functions of their atomic numbers, not atomic masses. This refined Mendeleev's table and resolved anomalies like Ar-K. The modern periodic table is thus based on Moseley's work. Mendeleev proposed the original table based on atomic masses. Newlands gave Law of Octaves. Meyer plotted atomic volume curve.
Explanation:
CNG stands for Compressed Natural Gas. It is primarily methane stored at high pressure. It is considered a cleaner fuel than petrol or diesel because it produces fewer pollutants like carbon monoxide and unburnt hydrocarbons, and it leaves no residue upon combustion.
Assertion (A): The first ionization energy of Nitrogen is higher than that of Oxygen. Reason (R): Nitrogen has a half-filled p-orbital which is exceptionally stable.
A.A is false but R is true.
B.Both A and R are true but R is NOT the correct explanation of A.
C.Both A and R are true and R is the correct explanation of A.
Explanation:
Nitrogen (1s2 2s2 2p3) has a exactly half-filled p-subshell, which confers extra stability due to symmetry and exchange energy. Oxygen (1s2 2s2 2p4) has one paired electron in the p-orbital, leading to electron-electron repulsion, making it easier to remove. Thus, N has a higher IE than O. Both are true and R explains A.
Explanation:
Use Charles' law: V₁/T₁ = V₂/T₂. T in Kelvin: T₁ = 27+273 = 300 K, T₂ = 327+273 = 600 K. V₂/V₁ = T₂/T₁ = 600/300 = 2. Volume doubles. The ratio is 2:1. Note that 27 to 327 is a 300°C increase, but absolute temperature doubles.
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