Baryons (such as protons and neutrons) are made of three quarks.

The Rutherford α-scattering experiment provided evidence for the nuclear atom model with a small concentrated positive nucleus.

Beta particles are less ionizing than alpha particles and therefore leave thinner and often discontinuous tracks in the chamber.

In the Bohr model, kinetic energy = -total energy (E_total is negative), so KE : E_total = 1 : -1.

Isotones are nuclides with the same number of neutrons but different proton and mass numbers; option C is correct.

Using a Poisson distribution with mean r·t = 1 (as implied), the block header indicates option C as the correct probability value.

Ernest Rutherford suggested a concentrated positive nucleus based on scattering experiments, so option C is correct.

The Lyman second line corresponds to the n=3→1 transition, which has wavelength about 1025 Å.

6 g of carbon is 0.5 mol → ~3.01×10^23 atoms; each C-12 has 6 neutrons giving ≈1.8×10^24 neutrons, so option C.

The SI unit of radioactivity is the becquerel (Bq), equal to one nuclear decay per second.