Who discovered the spin quantum number?

What does it mean if the $\alpha$-particle passes through the gold foil without any deviation?

Particles used in the Rutherford's scattering experiment to deduce the structure of atoms:

Explain Rutherford's argument for scattered $\alpha$-particles.

$A$ $7.9 \text{ MeV}$ $\alpha$-particle scatters from a target material of atomic number $Z = 79$. From the given data, the estimated diameter of the nucleus of the target material is (approximately) . . . . . . $\text{m}$.
$\left[\frac{1}{4 \pi \epsilon_0} = 9 \times 10^9 \text{ Nm}^2/\text{C}^2\right.$ and electron charge $\left.e = 1.6 \times 10^{-19} \text{ C}\right]$

Which source is associated with a line emission spectrum?