In the gold foil experiment, if one mole of $\alpha$- particle is bombarded on the gold foil, approximately $1.00\%$ of the alpha particles deflect at angles greater than $50°$, what is the number of $\alpha$-particles that would deflect at the angle is less than $50°$ ?

No. of particles bombarded $=1\mathit{ mole}=6.022\times {10}^{23}$particles

No. of $\alpha$-particles deflected at an angle $>50° =1\%$

Therefore, no. of α-particles deflected at an angle $<50° =100-1=99\%$

No. of α-particles deflected at an angle $<50° =\frac{99}{100}\times 6.022\times {10}^{23}=5.96\times {10}^{23}$

Therefore, no. of $\mathrm{\alpha }$-particles deflected at an angle $<50°$ is equal to $5.96\times {10}^{23}$.