What is Term symbol: Definition and 13 Discussions

In quantum mechanics, the term symbol is an abbreviated description of the (total) angular momentum quantum numbers in a multi-electron atom (however, even a single electron can be described by a term symbol). Each energy level of an atom with a given electron configuration is described by not only the electron configuration but also its own term symbol, as the energy level also depends on the total angular momentum including spin. The usual atomic term symbols assume LS coupling (also known as Russell–Saunders coupling or spin-orbit coupling). The ground state term symbol is predicted by Hund's rules.
The use of the word term for an energy level is based on the Rydberg–Ritz combination principle, an empirical observation that the wavenumbers of spectral lines can be expressed as the difference of two terms. This was later summarized by the Bohr model, which identified the terms (multiplied by hc, where h is the Planck constant and c the speed of light) with quantized energy levels and the spectral wavenumbers (again multiplied by hc) with photon energies.
Tables of atomic energy levels identified by their term symbols have been compiled by the National Institute of Standards and Technology. In this database, neutral atoms are identified as I, singly ionized atoms as II, etc. Neutral atoms of the chemical elements have the same term symbol for each column in the s-block and p-block elements, but may differ in d-block and f-block elements if the ground-state electron configuration changes within a column. Ground state term symbols for chemical elements are given below.

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  1. P

    Determining the term symbol of Sc

    I've solved further Term Symbol problems. The task is: derive the term symbols of the ground states of the following atoms: a) H, b) F, c) Cu, d) F- , e) P, f) Na, g) Sc Why is the d-orbital considered here in g)? Why isn't the s orbital taken into account here? The 4s orbital is energetically...
  2. P

    What levels result from a 4F term

    Hi everyone! I can't solve a problem. It is about the following task. How exactly should I proceed here? Task A): What levels result from a 4F term? How many states are there at each level? I tried many ways but none of them helped me to solve this problem. However, I have some basic ideas...
  3. Mr_Allod

    Hund's Rule for Determining Term Symbol Energy Order

    Hello there, for the above question I have no issue finding the term symbols but I am a little unsure about employing Hund's rules to the electron configuration, particularly those referring to the energies based on the total angular momentum J. These state: - In a less than ##\frac12##-filled...
  4. insanul

    Term Symbol of Carbon & Configuration Explanation

    A ground state configuration table for carbon is shown below. I am wondering why although configuration 4 and 5 share the same ML and MS ,they belong to different energy levels 1D2 and 3P2. It is just randomly chosen or they do have some rules? What cause the difference of energy levels of No.3...
  5. A

    Term symbol of a molecule in an excited state

    Homework Statement Considering the molecule of ##C_2^+## in an excited state with valence configuration ##2\sigma_g^2## ##2\sigma_u^2## ##1\pi_u^2## ##3\sigma_g^1##. Finding all the possible term symbol. Homework Equations Term symbol ##^{2S+1}\Lambda## ##L=0 \rightarrow \Sigma## ##L=1...
  6. W

    How does the Pauli Exclusion Principle in this problem?

    Homework Statement This is not a homework problem. It's an example in a textbook. 3 electrons. For ##S=3/2##, we have that $$ m_{s_1} = m_{s_2} = m_{s_3} = 1/2 $$ Therefore by the Pauli Exclusion principle, $$ m_{l_1} \neq m_{l_2} \neq m_{l_3} $$ and they take the values ##-1,0,1##...
  7. H

    I Why Is Crystal-Field Splitting Different for f-Orbitals Compared to d-Orbitals?

    There is several things I don't quite understand about crystal-field splitting. Q1: Why is crystal-field effect is not explained for f-orbitals like in d-orbitals in terms of real-orbitals? Correct me if I am wrong, but typically for d-orbitals, crystal-field splitting is explained classically...
  8. T

    How to pronounce this term symbol?

    $$5^{2}S_{\frac{1}{2}}$$ My guess is five-two-S-one-over-two. Any suggestion is appreciated. Thanks.
  9. bearcharge

    Pointless in talking about atomic term for a certain micro-state?

    I'm a chemist trying to understand atomic term symbol. If we list all the micro-states of certain multi-electron configuration, these micro-states can be grouped into several certain terms characterized by L and S. In other words, when we compute the ML and MS for each of the micro-state, they...
  10. A

    Term Symbol of np3 & np2: What Are They?

    For np3, there is a term symbol: 4S I think it is because l are -1,0 and 1 So, L value=-1+0+1=0 However, for np2 , there is not a term symbol: 3S (I assume l are -1 and 1) I know I misunderstand something, but what are they?
  11. E

    Lowest energy term symbol for nitrogen

    Homework Statement Lowest energy term symbols for Nitrogen Homework Equations L=l1+l2, l1+l2-1, l1-l2 S=s1+s2, s1-s2 J=S+L, S-L The Attempt at a SolutionSo I think I'm doing this right up until finding the J value. So the configuration of nitrogen is 1s22s22p3, so were working with 3...
  12. P

    Angle calculation from Atomic Term Symbol

    Homework Statement Calculate the smallest angle (in degrees) that the total angular momentum of an atom in a 7D term can make with the z-axis. Homework Equations 2S+1LJ The Attempt at a Solution Given that the total angular momentum of the atom is defined by the quantum number J...
  13. F

    Term Symbol for Carbon He2s^22p^2

    Term Symbol for Carbon Total Angular Momentum 1. Write the term symnbols for carbon atom He2s22p2 which has two equivalent p electrons taking into account the Pauli exclusion principle. 2... 3. Since the carbon has two equivalent p-electrons, we know the l1=1 and that l2=1 as well. Also the...