Acid rain is primarily caused by the oxides of: MCQ with Answer and Explanation

Explanation:
Compost is decomposed organic matter (plant waste, manure) and is an organic fertilizer. Urea, though organic compound, is considered a synthetic nitrogenous fertilizer when industrially produced. Organic fertilizers are derived from natural sources: manure, bone meal, compost. They improve soil structure. Ammonium nitrate, superphosphate are inorganic/synthetic. Urea is often categorized as synthetic organic.

Explanation:
The modern periodic law, established by Henry Moseley, states that the properties of elements are periodic functions of their atomic numbers. Mendeleev’s original table was based on atomic mass, but the modern version uses atomic number which resolves anomalies like Ar (Z=18, mass 40) and K (Z=19, mass 39).

Explanation:
Atomic number (Z) is the number of protons in the nucleus, which defines the identity of the element. In a neutral atom, the number of electrons equals Z. Neutrons contribute to mass number but not atomic number. Isotopes have same Z but different number of neutrons. Nucleons are total protons + neutrons = mass number. The modern periodic table is based on atomic number.