Which Electron Configuration Represents An Excited State

September 27, 2022 Webster West

The electron configuration that represent an excited state for an atom of calcium is 2, 8, 7, 3.

Calcium atom has an atomic number of 20 and its electronic configuration is 2, 8, 8, 2. An atom is said to be in an excited state if it gains energy and move to an higher energy level. For the calcium atom given above, there are 20 electrons which are distributed into four shells. But in the excited state [option 3], one of the 8 electrons in the third shell gains energy and move to the fourth shell. Thus, the number of electrons in the third shell reduced by 1, while the number of electrons in the fourth shell increase by 1. Advertisement Advertisement

Electronic configuration is defined as the systematic distribution of electrons in the shells of atom. The excited state of electrons in calcium is 2, 8, 7, 3.

Calcium is a chemical element with symbol Ca and atomic number 20. The electronic configuration of calcium is 2, 8, 8, 2. The electrons are excited when an electron enters in the energy state higher than its ground state.

In calcium, the excited state of electronic configuration is 2, 8, 7, and 3. The electron in the M shell gets excited and enters in the N shell.

Therefore, the electronic configuration in excited state of calcium is 2, 8, 7, and 3.

An atom is in the excited state if its electron occupies an orbital of a higher energy level or sublevel, before completely filling the orbital of a lower energy level or sublevel. Therefore, if a configuration of an atom deviates from ground state 1s$^2. configuration, we can say it is excited.

Ground state electronic configuration of Oxygen (8O)

The Periodic Table of elements tells us that there are a total of 8 electrons present in oxygen in its ground state.

These 8 electrons can be arranged using the standard notation as 1s2 2s2 2p4.

While placing electrons in their respective orbitals, we must follow the following three rules:

Aufbau principle: The electrons are filled in an increasing energy order. The closer a subshell is to the atomic nucleus, the lower its energy. This is because the positively charged nucleus will have a stronger hold on the negatively charged electrons present in that subshell. So, the electrons from the oxygen atom are first placed in 1s then 2s followed by 2p orbitals.

Which Electron Configuration Represents An Excited State

Hund’s rule: The electrons are first singly filled in the orbitals and then pairing occurs. For example, the p subshell has 3 degenerate atomic orbitals. So, the 4 remaining electrons of oxygen (after filling the lower energy 1s and 2s orbitals), are first placed in each of the 3 orbitals one by one and then the fourth is paired up (see the figure below).

Pauli exclusion principle: Each orbital can accommodate a maximum of two electrons only and these two electrons will be situated in an anti-parallel spin to minimize electronic repulsion.

Which Electron Configuration Represents An Excited State

The ground state electronic configuration of Oxygen can thus be represented as shown in the figure below.

Which Electron Configuration Represents An Excited State

The electronic configuration shows that the outer shell of oxygen (i.e., shell no 2) has a total of 6 electrons. So, oxygen has 6 valence electrons respectively.

Now, that we know its ground state electronic configuration, let’s find out how will we write its electronic configuration in the excited state.

Excited state electronic configuration of Oxygen (8O)

The electrons jump from the lower energy orbitals to higher energy orbitals by absorbing energy from an external source. As a result, the atoms achieve an excited state. The arrangement of electrons in the atom in this excited state is called the excited state electronic configuration.

Which Electron Configuration Represents An Excited State

Which Electron Configuration Represents An Excited State

We should note that on excitation the electrons can jump from a low-energy atomic orbital to any of the higher-energy orbitals. But, as a general rule of thumb, it is usually the least stable electron that undergoes excitation, and it jumps to an energy level such that the energy difference (∆E) between parent and host orbitals corresponds to the energy absorbed from an external source.

Which Electron Configuration Represents An Excited State

Example

The ground state electronic configuration of Carbon (6C) is:

1s2 2s2 2p2

One 2p orbital of carbon is still empty so upon excitation, one of the two 2s electrons is unpaired and shifted to the empty 2p orbital. So, the electronic configuration of 6C in its excited state becomes:

1s2 2s1 2p3

FAQ

What is the difference between the ground state and excited state electronic configurations?

Ground state

The ground state is the lowest energy electronic configuration of an atom.
It can be determined by identifying the element from the Periodic Table.
The electrons are filled in the atomic orbitals following the Aufbau principle, Hund’s rule, and Pauli exclusion principle respectively.

Excited state

The atoms achieve an excited state electronic configuration when electrons absorb energy and are shifted from a lower energy orbital to a higher energy atomic orbital.
It is usually an unstable electronic configuration.
Consequently, the electrons fall back to the ground state by releasing a specific amount of energy.

What is the electronic configuration of nitrogen in the first excited state?

The ground state electronic configuration of nitrogen (7N) is 1s2 2s2 2p3.
The 2p orbitals are not completely filled. There is still some space available.
So, the first excitation (by minimum energy absorption) makes a 2s electron jump to a 2p orbital.

Thus, the electronic configuration of nitrogen in its first excited state is 1s2 2s1 2p4 which is a very unstable configuration.

What is the excited state electronic configuration of sulfur?

The ground state electronic configuration of sulfur (16S) is 1s2 2s2 2p6 3s2 3p4 .
Excitation by energy absorption leads to an electron jump from the 3p to the higher energy 3d orbital. So, its electronic configuration becomes 1s2 2s2 2p6 3s2 3p3 3d1.
Upon further energy absorption, one of the 3s electrons also shifts to a 3d (the 3p electrons do not jump further because they are very stable in a half-filled 3p3 state).

So, the excited state electronic configuration of sulfur becomes 1s2 2s2 2p6 3s1 3p3 3d2

How do you write an excited state electronic configuration for sodium?

The ground state electronic configuration of sodium (11Na) is 1s2 2s2 2p6 3s1.
Upon excitation, the 3s electron shifts to its adjacent 3p orbital so the electronic configuration of sodium in this excited state becomes 1s2 2s2 2p6 3s0 3p1.
This is a very unstable configuration so the 3p electron readily moves back to 3s, releasing energy equal to 580 nm. This wavelength corresponds to the yellow color of a sodium vapor lamp.

Which of the following electronic configurations represents an excited state for a potassium atom?

1s2 2s2 2p6 3s2 3p5 4s1
1s2 2s2 2p6 3s2 3p5 4s2
1s2 2s2 2p6 3s2 3p6 4s1
1s2 2s2 2p6 3s2 3p6 4s2

The ground state electronic configuration of potassium ( 19K ) is 1s2 2s2 2p6 3s2 3p6 4s1
There is a space for one more electron in the 4s orbital.
So, upon excitation, one of the 3p electrons absorbs energy and jumps to the adjacent 4s orbital.

Thus, the electronic configuration of a potassium atom in its first excited state is 1s2 2s2 2p6 3s2 3p5 4s1 which is option ii.

Which of the following electronic configuration shows that the atom is in an excited state?

1s2 2s1
1s2 2s2 2p4
1s2 2s2
1s2 2s2 2p6 3s2
1s2 2s2 3s1

Option 5 is the correct answer. There is a 2p orbital before a 3s orbital. If an electron shifts from a 2p to a 3s orbital, the ground state electronic configuration 1s2 2s2 2p1 of Boron (5B) becomes 1s2 2s2 2p0 3s1 or simply 1s2 2s2 3s1.

An excited state means that (typically) the valence electron has moved from its ground state orbital (i.e. lowest available energy) to some other higher energy orbital.

For example, if we look at the ground state (electrons in the energetically lowest available orbital) of oxygen, the electron configuration is #1s^2 2s^2 2p^4#. If the element were to become excited, the electron could occupy an infinite number of orbitals. However, in most texts the example will be the next available one. So for oxygen, it might look like this: #1s^2 2s^2 2p^3 3s^1# – where the valence electron now occupies the 3s orbital in an excited (i.e. not ground) state.

So any electron configuration in which the last electron (again, the valence electron) is in a higher energy orbital, this element is said to be in an excited state.

FAQ

Which of the following represents an excited state?

An excited state configuration is a higher energy arrangement (it requires energy input to create an excited state). Valence electrons are the electrons utilised for bonding. These are the ‘outer’ electrons (i.e. the electrons which travel furthest away from the nucleus) and the highest energy electrons.

Which electron configuration represents an excited state for an atom of potassium?

1s22s22p53s1.