The decay constant for a radioactive nuclide is $$1.5 \times 10^{-5}$$ s$$^{-1}$$. Atomic weight of the substance is 60 g mole$$^{-1}$$, $$N_A = 6 \times 10^{23}$$. The activity of 1.0 $$\mu$$g of the substance is _______ $$\times 10^{10}$$ Bq.

Given: $$\lambda = 1.5 \times 10^{-5}$$ s$$^{-1}$$, atomic weight $$M = 60$$ g/mol, mass = 1.0 $$\mu$$g = $$10^{-6}$$ g.

Number of atoms:

$$N = \frac{m}{M} \times N_A = \frac{10^{-6}}{60} \times 6 \times 10^{23} = 10^{16}$$

Activity:

$$A = \lambda N = 1.5 \times 10^{-5} \times 10^{16} = 1.5 \times 10^{11} = 15 \times 10^{10} \text{ Bq}$$

The activity is 15 $$\times 10^{10}$$ Bq.