When two hydrogen atoms get close enough, the electron from each atom feels an attraction from the proton in the other atom's nucleus. This attraction pulls the atoms together. The electrons end up ...

For elements in the first three periods of the periodic table (hydrogen ... and so electrons go into the 4s orbital before occupying the 3d orbitals. Consequently, potassium and calcium have the ...

Nature of electromagnetic radiation, photoelectric effect, spectrum of the hydrogen atom, Bohr model of ... exclusion principle andHund'srule, electronic configuration of elements and extra ...