Which of the following is a compound? MCQ with Answer and Explanation

Explanation:
Ernest Rutherford, in 1911, along with Geiger and Marsden, bombarded a thin gold foil with alpha particles. Most passed through, some were deflected at large angles, leading to the nuclear model of the atom—a small, dense, positively charged nucleus with electrons around it. Thomson's plum pudding model predicted no large deflections. Chadwick discovered neutron.

Explanation:
The maximum number of electrons in a shell is given by the formula 2n², where n is the principal quantum number. For the N shell, n = 4. Thus, maximum electrons = 2(4)² = 2(16) = 32. The K, L, M, and N shells hold 2, 8, 18, and 32 electrons respectively.

Explanation:
NPK stands for Nitrogen (N), Phosphorus (P, as P₂O₅), and Potassium (K, as K₂O). These are primary macronutrients essential for plant growth. The numbers on a fertiliser bag (e.g., 10-26-26) indicate the percentage of N, P₂O₅, and K₂O.