Energy of Orbitals, Hydrogen, Multi-Electron Atom, Factors Affecting the Orbital Energy (For CBSE, ICSE, IAS, NET, NRA 2022)

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Energy of Orbitals

  • The energy of orbitals refers to the energy required to take an electron present in that orbital to infinity or the energy released when an electron is added to that orbital from infinity. The energy of orbital depends on principle quantum number (n) and azimuthal quantum number (l) i.e.. , it depends on shell and subshells.
  • Electrons are negatively charged and have their own energy. The energy of an electron defines which orbit it will be in.
  • For orbitals belonging to the same subshell, it is same and those orbitals with the same energy are known as degenerate orbitals.
Energy of Orbitals

Energy of Orbitals

Energy of Orbital in Hydrogen (Single-Electron Atom)

  • The exception to the general behaviour of the energy of orbitals as explained above is observed in Hydrogen, the energy of orbital is only dependent on principal quantum number, and so the 2s and 2p orbital in hydrogen atom have the same energy.
  • The 1s orbital in hydrogen atom corresponds to the most stable condition and is called ground state whereas any other orbital afterwards has higher energy than that of 1s orbital and are called excited state.

Energy of Orbital in Multi-Electron Atom

  • Unlike hydrogen (single-electron atom) , multi-electron atoms tend to have a different energy in different subshells of the same shell. The energy of orbital in these types of atoms is dependent on both principal quantum number (n) or shells and azimuthal quantum number (l) or subshells. That is, for a given principal quantum number like 3, the different subshells 3s, 3p and 3d will have different energies.
  • The reason behind different energies between the various subshells of the same shell is that there exists a mutual repulsion among the electrons in multi-electron atoms. The stability of multi-electron atom is due to the bigger magnitude of attractive force between nucleus and electrons as compared to the forces of repulsion between electrons of the inner shell and outer shell.
  • Due to the presence of electrons in the inner shell, the outer shell electrons are not able to experience a full positive charge of the nucleus. This effect is known as the shielding effect and the net nuclear charge felt by an outer shell electron is known as an effective nuclear charge.

Factors Affecting the Orbital Energy

  • The s orbital electron will be more tightly bound to the nucleus as compared to the p orbital electron, which is more tightly bound in regard to a d orbital electron for a given value of the principal quantum number.
  • As compared to p orbital electrons, s orbital electrons will have more negative or lesser amount of energy. Here, the p orbital electrons will have lesser energy than that of d orbital electrons.
  • As the extent of shielding from the nucleus is different for the electrons in different orbitals, it leads to the splitting of energy levels that have the same principal quantum number. Therefore, the orbital energy would depend on the values of both the principal quantum number and azimuthal quantum number, symbolized as n and l respectively. Hence, the lower value of for an orbital, the lower is its energy.
  • With the increase in the atomic number (Zeff) , the orbital energy decreases in the same subshell.


What is the Energy of an Orbital?


The energy of orbitals refers to the energy required to take an electron present in that orbital to infinity or the energy released when an electron is added to that orbital from infinity.

What Orbital Has the Highest Energy?



In all the chemistry of the transition elements, the 4s orbital behaves as the outermost, highest energy orbital. The reversed order of the 3d and 4s orbitals only seem to apply to building the atom up in the first place. In all other respects, the 4s electrons are always the electrons you need to think about first.

What is the Lowest Energy Orbital?


At the lowest energy level, the one closest to the atomic center, there is a single 1s orbital that can hold 2 electrons. At the next energy level, there are four orbitals; a . Each of these orbitals can hold 2 electrons, so a total of 8 electrons can be found at this level of energy.

What is Energy Level Diagram?


Energy level diagrams are a means of analyzing the energies electrons can accept and release as they transition from one accepted orbital to another.

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