If an electron is moving in the n^th orbit of the hydrogen atom, then its velocity (v_n) for the n^th orbit is given as :

Which level of the single ionized carbon has the same energy as the ground state energy of hydrogen atom?

Calculate the time interval between 33% decay and 67% decay if half-life of a substance is 20 minutes.

The half-life of Au¹⁹⁸ is 2.7 days. The activity of 1.50 mg of Au¹⁹⁸ if its atomic weight is 198 g mol^$$-$$1 is, (N_a = 6 $$\times$$ 10²³/mol).