Electron Configuration

Introduction

The distribution of electrons within an atomic subshell is described by the electronic configuration. The overview of prediction of the position of the electrons surrounding a nucleus is called an electron configuration. The electron no. in every neutral atom is the same as the proton no. Now, we'll organize those electrons such that they stand about the nucleus which shows their energy and the orbital type in which they are situated. Depending on their energy, electrons occupy orbitals in a certain order.

What are Electronic Configurations?

• The distribution of electrons within an atomic subshell is described by the electronic configuration.

• Atomic electronic configurations adhere to a standard way in which each atomic subshell that contains an electron is listed in order.

• The usual representation of electronic configuration may be rather lengthy for high atomic numbers. In certain circumstances, an abridged/condensed symbol may be used in place of the conventional representation.

• The Na’s electron configuration, for instance, is $\mathrm{1s^2 2s^2 2p^6 3s^1}$.

Subshells

• The distribution of electrons into subshells is determined by the azimuthal quantum no., symbolized by the letter "l."

• The magnitude of the principal quantum no., n, dictates the magnitude of this quantum number. As a result, four distinct subshells can exist when n is equal to 4.

• The s, p, d, & f subshells, accordingly, relate to l=0,1,2, 3 quantities for n = 4.

• The highest electrons no. that a subshell may hold is given by the equation 2(2l+1)

• The greatest number of electrons that the s, p, d, & f subshells can accommodate is 2, 6, 10, and 14 respectively.

Writing the Electronic Configuration

The writing of electronic configuration is governed by three sets of regulations. They regulate how each element's electronic configuration is established. Energy states are distances where the energy of the electrons' rotations around the nucleus is known. With a rise in distance from the nucleus, and energy state's associated energy rises. However, the electron energy level diagram for many-electron configurations is difficult for all to recall.

However, by comprehending the Aufbau concept, one may describe the electron configuration. According to the n+l rule, the electrons in the atomic orbitals of an atom in the least energy state occupy them in the sequence of increasing energies. The energy increases with the orbital's n+l value. If 2 orbitals have the identical no. for n+l, the electrons will initially fill the orbital with n's smaller value since it has the lesser energy. Therefore, the electrons occupy this sequence −

$$\mathrm{1s,2s,2p,3s,3p,4s,3d,4p,5s,4d,5p,4f,5d,6p,7s…}$$

Only two electrons with the opposite spin may fit in each atomic orbital.

Thus, the first shell may contain two electrons in a 1s. Two in 2s & six in 2p, a total of 8 electrons may be found in the second shell.

Additionally, the above-mentioned principles are followed when placing the electrons in these orbitals in the sequence.

Filling of Atomic Orbitals

The following concepts govern how the electrons in the atomic orbitals are occupied.

Aufbau Principle

The energy of an atomic orbital is determined by summing the principal as well as azimuthal quantum no., & according to the Aufbau principle, electrons first enter relatively low energy orbitals while going to greater energy orbitals.

Chris Evans, Dr. Roger Peters, Dr. Mike Thompson, Chris Gadsby, Ken Partridge, Roy Mylan, Yehoshua Sivan, Tom Nation, Dr. David Follows, Vikash Hemnath Seeboo, Aufbau, CC0 1.0

Pauli Exclusion Principle

According to this principle, only electron pairs with opposite spins may be carried in an atomic orbital, and no two electrons in the identical atom have identical values for all 4-quantum no.

2 electrons should have opposing spins if they have the identical principle, azimuthal, & magnetic no.

Hund’s rule

Each orbital in a particular subshell is said to be solely filled by electrons before a 2nd electron is placed in an orbital.

Representation of Electronic Configuration of Atom

In this section, examples of a few elements' electronic configurations are given.

Hydrogen's electron configuration

H has an atomic no. of 1. So, an H atom has 1 electron, which will be assigned to the first shell/s orbit's subshell. H electronic configuration is 1s¹.

BruceBlaus, Blausen 0529 HydrogenAtom, CC BY 3.0

Chlorine's electron configuration

The atomic no. of Cl is 17. As a result, its 17 electrons are divided as −

2 electrons in the K

8 electrons in the L

7 electrons in the M

The following shows how Cl's electron configuration looks. It can be expressed as $\mathrm{1s^2 2s^2 2p^6 3s^2 3p^5}$.

Pumbaa (original work by Greg Robson), Electron shell 017 Chlorine, CC BY-SA 2.0 UK

Conclusion

It can be concluded that Electron configuration is the depiction of electron distribution inside an element's atomic shells. The configuration assists in determining the position of these electrons since the electrons are mathematically positioned in these subshells. According to their electron configurations, the periodic table divides elements into 4 categories. The s, p d, & f-block elements are composed of these. The principal quantum no. determines the maximum no. of electrons that can fit in a shell (n). The distribution of electrons into subshells is determined by the azimuthal quantum number, symbolized by the letter "l."

FAQs

1. What are the exceptions to the constraints governing electronic configuration?

Chromium & copper are the 2 main exceptions to the electronic configuration rule. In these situations, a fully/half-filled d-subshell electronic configuration is more stable than one that is only partially filled, which causes an excited electron from the 4s orbital to climb to the 3d orbital.

2. In the n=3 energy state, what subshells are feasible? At this level, how many orbitals are feasible?

We are aware that the no. of subshells depends on the Azimuthal quantum no. l has the values 0, 1, & 2 given n=3. Therefore, at the n=3 energy state, 3 subshells—s, p, & d—are conceivable.

We have 3 subshells—the s, p, as well as d subshells—for the n=3 energy level. The s subshell has one orbital, as far as we know, p possesses three orbitals, but the d subshell has five. Thus, there are nine orbitals altogether at the n=3 energy level.

3. Why is it vital for elements to have specific electron configurations?

By identifying an atom's valence electrons, electron configurations can shed light on its chemical behaviour. Additionally, it assists in organizing elements into different blocks like s,p,d, and f blocks.

4. List the importance of electron configuration.

The significance is described below −

They assist in determining the atom's reactivity state.

It aids in identifying both its chemical and physical characteristics.

It foretells an atom's magnetic properties.

5. Which subshells are present for n=3?

One orbital may contain a maximum of 2 electrons, and there are 4 subshells present- s, p, d, as well as f for n=3. Maximum no. of orbitals corresponding to s,p,d and f subshell are 1,3,5 and 7.