This question is an exact duplicate of:
- Energy levels in molecules 1 answer
when atoms are well seperated energy spectrum is discrete, but when they come together energy levels split and they form bands, upto this i can understand. where im confused is that these splitting of energy levels corresponds to each individual atoms or molecule as a whole. for example if we consider two hydrogen atoms seperated by large distance energy levels are discrete, now when they come together 1s level of hydrogen molecule is two seperate 1s levels, here im confused that 1s level of each atom split into two and both hydrogen atoms in total have 4 energy levels or combined hydrogen molecule will have two 1s levels, having one 1s level for each hydrogen atom which are seperated by some energy gap.