A radioactive element has decay constant $\lambda$ (expressed in s^–1). The number of nuclei of this element at t = 0 is N. What is the expected number of nuclei that will have decayed after 1 s?

A.  $N\left( {1 - {e^{ - \lambda }}} \right)$

B.  $\frac{N}{\lambda }$

C.  $N{e^{ - \lambda }}$

D.  $\lambda N$

A