The excited state of electron is responsible for many properties exhibited by it. It is the basis of atomic chemistry and molecule formation. This article illustrates interesting facts related to the excitation phase of the electrons.
The excited state of electron can be defined as the temporary movement of an electron from its ground state to an excited state on the provision of extra energy. This excited state of electron can be achieved by transference of energy in the form of collision between molecules, absorption of a photon, packet, or light.
For understanding the excited state of electron it is mandatory to look out for the energy framework of an atom. An atom comprises 3 entities namely neutrons, protons, and electrons. The nucleus consists of protons and neutrons which are surrounded by electrons in well-defined shells known as energy levels which have varying energies. This is the ground state description of an atom where the electrons are in the state of lowest energy.
Every orbital has specific energy parameters. For an electron to be excited it needs to move from its lowest stable energy level to the higher unstable energy level. This can only be possible if the electron overcomes the energy difference between both the orbital. This can be possible only if a photon of that much energy capacity is absorbed by the electron. Fulfillment of this energy requirement leads to the ideal condition for excited state of electron. But this excited state of electron is transient and within a few milliseconds electrons return to their ground state from the excited state with the emission of the photon.
Apart from the excited state of electron, there is also a possibility of the electron achieving the maximum energy where the nuclear attraction or nuclear energy has no role to play. That excited state electron is the ionized electron. There are many facts associated with the excited state of electron which is discussed ahead:
- Electronic configuration of the excited state of electron
- When is the excited state of electron?
- How is the excited state of electron is formed?
- Role of electronic configuration in determining the excited state of electron
- Formula of electronic configuration during the excited state of electron
- The time of excited state electron
- Changes in electron during the excited state of electron
- The first excited state of electron
- Calculation of first excited state of electron
- Level of first excited state electron
- Validity of excited state of electron
Electronic configuration of excited state electron
The electronic configuration is the arrangement of electrons in the energy levels according to the stability. Usually, the electronic configuration of every element depicted in the periodic table is in its ground state. During the bonding of elements to form various compounds, there is sharing, gaining, and losing of electrons which leads to an excited state of electron formation.
Excited state electrons are formed by the input of energy and are always in a higher arrangement. It is demonstrated with the help of an example. For instance, let us consider oxygen having an atomic number = 8. Its electronic configuration in the ground state or lowest most stable energy form is 1s22s22p4. If the oxygen is to be excited then it can occupy an infinite number of orbitals, but usually, they occupy the next orbital. So in the excited state, the electronic configuration of oxygen will be 1s22s22p33s1
When is the excited state of electron?
The excited state of electron happens because the valence electrons or the outermost electrons do not always remain in their respective shells. Due to the absorbance of heat, light, or quanta, they jump to a higher energy level that is far away from the nucleus. But this phenomenon is not permanent. The excited electron comes back to its original position losing energy thereby calling it the process of emission.
How is the excited state of electron is formed?
The process of formation of the excited state of electron is similar as explained above. It involves the absorption and emission of energy which leads to excitation and then retrieval of electrons back to their ground state. The minimum energy required for the movement of electron is the threshold energy. It is the difference between ground state and the excited state. This complete procedure happens in a confined wavelength which in turn emits colored radiations thereby forming spectra.
For instance copper metal when heated in a hot flame then the color of the flame is bright green. This is justified by the excited state of electron followed by emission.
Role of electronic configuration in determining the excited state of electron
The electronic configuration is affected by the excited state of electron. The electronic configuration of an atom where there is excitation shows the movement of valence electrons to the next higher orbital.
For instance Sodium metal is a metal that has the atomic number 11. Its ground state electronic configuration is 1s22s22p63s1. During excitation, the electron present in the 3s sublevel will get promoted to the 3p sublevel. So the excited state electronic configuration will be 1s22s22p63p1. But this is a very unstable condition and the excited state of electron will not be long-lived before returning to its original electronic configuration.
This whole procedure of excitation and coming back to its original state results in releasing of a characteristic yellow flame in the case of sodium metal.
Formula of electronic configuration during the excited state of electron
There are no formulas or hard and fast rule to determine the electronic configuration of the excited state of electron. The only important thing to be aware of is how to write the electronic configuration of elements with proper energy distribution. The excited state of electron then can be achieved by jumping the electron to the adjacent higher energy level which is short-lived.
The time of excited state electron
The excited state of electrons is a very short-lived period due to the instability in energy distribution. In most of the atoms, the average time before the emission process is 10-9 to 10-8 seconds. The only excited state which can stay for a long time is the metastable state. Though the time is less than the ground state, it is much more than the other excited state of electron. The considerable time in the metastable state is 10-6 to 10-3.
Changes in electron during the excited state of electron
The concept of what happens to electrons when it is excited is very complex and has different theories and notions. Many scientists and researchers believe that the electrons themselves do not move from one shell to another but many of them disagree
They work on this notion that an atom is not an object as explained by the classical theory but it is in the form of a wave as explained by later developed quantum theory. It is proposed that there is the movement of electrons in many molecular excitations like n to pi* where initial and final states have different wavefunctions. This topic touches the wave like aspect of the orbital where energy is in the form of quanta.
The first excited state of electron
The first excited state of electron in an atom can be explained as when the electrons in the ground state get sufficient energy to jump to the next orbital. For example
In the H atom, electrons occupy shells denoted as n. The ground state then is n=1 and above that is the first excited state of electron n=2.
The energy difference is given by
En = -13.6eV/n^2 where n = 1, 2, 3, 4….
So the energy difference of the first excited state of electron can be E2-E1 = 10.2eV
Calculation of first excited state of electron
Energy calculation of the excited state of electron is usually done for hydrogen-like atoms which have only one electron. The energy of the nth level can be calculated as
En = -Z2 x 13.6eV/ n2 where Z is the atomic number of the atom.
Presence of 1 electron means that the electronic configuration will be 1s1
So, E1 = -Z2 x 13.6eV/12
Hence the first excited state of electron energy level will be 1s02s1.
Level of the first excited state of electron
The level of the first excited state of electron can be judged with the help of energy levels proposed by Neil Bohr in his hydrogen atom model. Energy levels are denoted by n where n=1 is considered the ground state and n = 2 is the first excited state of electron. He also emphasized the fact that each electron in an atom can achieve its maximum energy and can still be part of the atom.
Validity of excited state of electron
Validation of the excited state of electron is done using density functional theory (DFT) using either a real space grid or a plane wave basis set. This concept is quite complex and is considered under the research category.
To summarize the excited state of electron is a condition when an electron jumps from its ground state to a higher excited state when provided with energy more than threshold energy in the form of packets of light or heat. This transient state is short lived and the similar amount of energy is emitted on reversal when atom drops from excited state to ground state. This process generates various spectra on the basis of the element involved.