The radius of the smallest electron orbit in hydrogen-like ion is $(0.51/4 \times 10^{-10})$ metre; then it is
hydrogen atom
$H^+$
$Li^{2+}$
$Be^{3+}$
In Bohr model of hydrogen atom, the force on the electron depends on the principal quantum number as
If in Rutherford’s experiment, the number of particles scattered at ${90^o}$ angle are $28$ per min, then number of scattered particles at an angle ${60^o}$ and ${120^o}$ will be
The gravitational attraction between electron and proton in a hydrogen atom is weaker than the coulomb attraction by a factor of about $10^{-40} .$ An alternative way of looking at this fact is to estimate the radius of the first Bohr orbit of a hydrogen atom if the electron and proton were bound by gravitational attraction.
In Bohr model of hydrogen atom, the force on the electron depends on the principle quantum number as
What is head-on collision ? For that tell the impact parameter.