Atomic Structure

Energy of the electron in hydrogen in its first orbit is:
An alpha particle after passing through a potential difference of $$2\times 10^6$$ volt falls on a  solver foil. The atomic number of silver is $$47$$.
A neutral atom of an element has a nucleus with nuclear charge $$11$$ times and mass $$23$$ times that of hydrogen.
In Balmer series of lines of hydrogen spectrum, the third line from the red end corresponds to which one of the following inter-orbit jumps of the electrons for Bohr's orbits in an atom of hydrogen?
It is not possible to measure the atomic radius precisely since the electron cloud surrounding the atom does not have a sharp boundary. One practical approach to estimate the size of an atom of a non-metallic element is to measure the distance between two atoms when they are bound together by a single bond in a covalent molecule and then dividing by two. For metals, we define the term "metallic radius" which is taken as half the internuclear distance separating the metal cores in the metallic crystal. The van der Waal's radius represents the overall size of the atoms which includes its valence shell in a non bonded situation. It is the half of the distance between two similar atoms in separate molecules in a solid. The atomic radius decreases across a period and increases down the group. Generally, same trends are observed in case of ionic radius. The ionic radius of the species having the same number of electrons depends on the number of protons in their nuclei.