Quantum number can be said to be an attribute, which refers to the influence of boundary conditions or box normalization on the discretization of physical quantities, and this * * * attribute is possessed by no matter how many atoms.

So 1 and quantum number can describe an atom or a group of atoms.

2. Excited states can describe an atom or a group of atoms.

You are absolutely right. A group of hydrogen atoms with n=4 can emit photons with six frequencies, while a hydrogen atom with n=4 can only emit photons with three frequencies at most.

Let's analyze it carefully:

Strictly speaking,

A hydrogen atom with n=4 may theoretically emit photons with six frequencies, but in fact it can only emit photons with three frequencies at most.

The reason is simple, because it can only emit three photons at most! Although there are six possibilities in theory. Speaking of which, you should understand ~

This is because, in theory, it has six possibilities of permutation and combination, but when 4->; Once it happens, 4-> 3, 3- > This is impossible. They are mutually exclusive events.

For example, if you take 10 yuan to the canteen, there are dozens of dishes on the menu, the most expensive 10 yuan and the cheap 5 yuan.

Before you buy a meal, you have all the possibilities on the menu.

But once you buy $ 10, you can't eat $5. or vice versa, Dallas to the auditorium

So you can only eat two kinds of dishes at most. Two fives, please.

But a group of people is different. Even if everyone only has 10 yuan, as long as there are enough people, you can eat all the dishes on the menu.

Please understand carefully.