किसी तत्व की द्रव्यमान संख्या (mass number) को किस प्रकार परिभाषित किया जाता है?

According to Heisenberg's Uncertainty Principle (Δv · Δx ≥ h4πm), what is the minimum value of Δv · Δx for an object of mass 10-6 kg? (Given h = 6.626 × 10-34 J s)

The number of orbitals associated with 'N' shell of an atom is:

Calculate the radius of the third orbit of He+.