Confusion about electron energy levels

In summary: The Aufbau Principle states that an electron in a higher energy orbitals has more potential energy than an electron in a lower energy orbitals.
  • #1
Yashbhatt
348
13
If 4s orbital is in the 4th shell and 3d is in the 3rd shell and if the Principal Quantum Number is the direct indication of the amount of energy in of the electrons in that shell. Then, why according to Aufbau principle is 4s filled before 3d?
 
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  • #2
Because an atom's energy doesn't depend on one quantum number only. In other words, if you model the electronic configuration of the multi-electron atom/ion as to resemble the hydrogen's, then there are other effects to take into account (spin, special relativity, screening of the nuclear charge by the inner electrons). There's no 100% accurate theoretical description of the Aufbau Principle, but there are rigorous arguments in favor of it.
If all was simple, then 1s < 2s < 2p < 3s < 3p < 3d < 4s < 4p < 4d < 4f < 5s < 5p < 5d < 5f < 5g < 6s ... would be the normal energy diagram (as for the plain simple H-atom/hydrogenic ions in Schrödinger's description), but due to a myriad of effects (symmetry of the spin-spin couplings between electrons, special relativity), we have these inversions: 1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s < 4f < 5d < 6p < 7s ...
 
  • #3
What are the arguments?
 
  • #4
For seeing whether that which orbital has higher energy there a formula in which we have to calculate n+l where n is Principal quantum number and l is Azimuthal quantum number.
Orbital having more value of n+l has high energy.
If value of n+l is equal for two orbitals than orbital having higher principal quantum number has higher energy.
 
  • #5
Murtuza Tipu said:
For seeing whether that which orbital has higher energy there a formula in which we have to calculate n+l where n is Principal quantum number and l is Azimuthal quantum number.
Orbital having more value of n+l has high energy.
If value of n+l is equal for two orbitals than orbital having higher principal quantum number has higher energy.

Okay. But that seems to be against the notion: The farther you pull an electron from the nucleus, the more potential energy it has.
 

1. What are electron energy levels?

Electron energy levels refer to the specific energies that electrons can have in an atom. These levels are determined by the amount of energy an electron has and its distance from the nucleus of the atom. The closer an electron is to the nucleus, the lower its energy level will be.

2. How many energy levels do electrons have?

The number of energy levels an electron can have varies depending on the type of atom. Generally, atoms can have anywhere from one to seven energy levels. For example, hydrogen has one energy level, while carbon has two, and potassium has seven.

3. Why do electrons have different energy levels?

Electrons have different energy levels because of the way they interact with the positively charged nucleus of an atom. The closer an electron is to the nucleus, the stronger the attraction and the lower its energy level. As electrons gain energy, they move to higher energy levels further from the nucleus.

4. How are electron energy levels related to an atom's properties?

The number and arrangement of an atom's energy levels determines its chemical and physical properties. For example, atoms with filled outer energy levels tend to be stable and unreactive, while atoms with partially filled outer energy levels are more likely to form chemical bonds with other atoms.

5. Can electrons move between energy levels?

Yes, electrons can move between energy levels. When an electron absorbs or releases energy, it can move to a higher or lower energy level, respectively. This process, known as electron excitation and de-excitation, is the basis of many chemical and physical phenomena, such as light emission and chemical reactions.

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