Mendeleev's periodic table had anomalies because he arranged elements by:
A. Atomic mass
B. Electronegativity
C. Density
D. Atomic number
Answer: Option A
Solution (By JKSSB Mock Tests)
Mendeleev used atomic mass as basis. Anomalies like Ar (mass 40) placed before K (mass 39) occurred. These were resolved when Moseley proposed atomic number as the basis.
Explanation:
COâ‚‚ is a major greenhouse gas that absorbs infrared radiation and re-emits it, warming the atmosphere. Other GHGs: CHâ‚„, Nâ‚‚O, water vapor, CFCs. Nâ‚‚ and Oâ‚‚ are diatomic homonuclear molecules that do not absorb IR and are not GHGs. Hydrogen is not a GHG. The increase in COâ‚‚ due to human activities is driving climate change.
Explanation:
Ozone (O₃) is a molecule consisting of three oxygen atoms, all of the same element. H₂O and CO₂ are compounds; NaCl is an ionic compound (not a discrete molecule). O₂ is also a molecule of an element.
Explanation:
Highly reactive metals like sodium, potassium, calcium, and aluminum cannot be reduced by chemical reducing agents like carbon. They are extracted by the electrolysis of their molten chlorides or oxides. For example, sodium is extracted by the electrolysis of molten NaCl in the Down's cell.
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