Discuss atomic radii being determined by the amount of electric charge in the nucleus. Hydrogen with only 1 proton has a radius of 1x10^-15 m, while helium, atomic number 2, has a radius of .62x10^-11 m. Explain the difference as a factor of the nuclear electric attraction. View lithium from the periodic table and note its radii, even smaller. State the reason why the radii are becoming smaller with increasing atomic number.Note that heavier elements are not much larger in radius than lighter elements. Discuss the emission of x-rays as electrons transition from one energy level to another. Recall that x -rays are electromagnetic, and the moving charge creates a magnetic field, also.