Electronic Configuration Of Elements

Introduction to Electronic Configuration of Elements in Chemistry

Knowledge of electronic configuration in elements is central to chemistry since it acts as a roadmap for properties/behaviour and reactivity of elements. Atoms are made up of a nucleus with protons neutrons and electrons that revolve around the nucleus in orbits known as shells. These electrons are placed in a manner that obeys certain regulations as constrained by quantum mechanics known as the Pauli exclusion principle, Hund’s rule and the Aufbau rule. The electronic configuration of an element defines how the respective element possesses electrons in the mentioned energy levels or orbitals defined by the quantum numbers; the principal quantum number (n), the azimuthal quantum number (l), the magnetic quantum number(ml), and the spin quantum number (ms).This allocation not only defines its chemical activity and connection abilities but also describes its placement and functioning scope within a periodical table.

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This Story also Contains

1. Electronic Configuration of Elements-
2. Solved Examples Based On Electronic Configuration of Elements
3. Conclusion

In this article, we will cover the concept of Electronic Configuration of Elements. This concept falls under the broader category of Atomic structure, which is a crucial chapter in Class 11 chemistry. It is not only essential for board exams but also for competitive exams like the Joint Entrance Examination (JEE Main), National Eligibility Entrance Test (NEET), and other entrance exams such as SRMJEE, BITSAT, WBJEE, BCECE and more.

Let us study in detail the Electronic Configuration of Elements to gain insights into this topic and solve a few related problems.

Electronic Configuration of Elements-

Writing of electronic configuration of any element is based on three rules as told in previous concepts. They are:

1. Aufbau principle

2. Pauli’s exclusion principle

3. Hund’s rule of maximum multiplicity

The distribution of electrons into orbitals of an atom is called its electronic configuration.

The electronic configuration of the different elements can be represented in two ways:

1. Subshell notation

2. Orbital diagram

Let’s understand with the help of examples:

1. The hydrogen atom has only one electron which goes into the orbital with the lowest energy, namely 1s. The E.C of hydrogen is 1s¹ (subshell notation)

Orbital diagram:

2. The electronic configuration of lithium is 1s² 2s¹. Lithium has 3 electrons, as its atomic number is 3. 2 electrons filled in 1s orbital and 1 electron filled in 2s orbital.

let us consider fluorine (Z = 9) :

F(Z = 9) = 1s², 2s², 2px², 2py², 2pz¹ or

The importance of knowing the exact electronic configuration of an element lies in the fact that the chemical properties of an element are dependent on the behaviour and relative arrangement of its electrons.

Recommended topic video on (Electronic Configuration of Elements)

Solved Examples Based On Electronic Configuration of Elements

Example 1: The electronic configuration of copper is:

1) (correct) [Ar]3d¹⁰4s¹

2) [Ar]3d⁹4s²

3) [Ar]3d¹⁰4s²

4) [Ar]3d⁸4s²

Solution: Ideally, the electronic configuration of Cu must be [Ar] 3d⁹ 4s² but in this case, the electrons in d-orbitals are not symmetrically filled. Thus to maintain the symmetricity, one electron from the 4s-orbital goes to the d-orbital and thus Cu maintains the electronic configuration as [Ar] 3d¹⁰ 4s¹.

Hence, the answer is the option (1)

Example 2: Which law indicates the pairing of electrons in the same orbital?

1) Newton’s first law

2) (correct) Hund’s rule

3) Aufbau principle

4) Pauli exclusion principle

Solution: Hund’s rule states that “pairing of electrons in the orbitals belonging to the same subshell (p, d or f) does not take place until each orbital belonging to that subshell has got one electron each. It is singly occupied”.

Hence, the answer is the option (2).

Example 3: In which of the following pairs, the outermost electronic configuration will be the same?

1) (correct) Cr+and Mn2+
2) V2+ and Cr+
3) Ni2+ and Cu+
4) Fe2+ and Co+

Solution: The outermost electronic configurations-
Cr+→[Ar]3d5Mn2+→[Ar]3d5
V2+→[Ar]3d3Cr+→[Ar]3d5
Ni2+→[Ar]3d8Cu+→[Ar]3d10

In Cr+and Mn2+, the outermost electronic configuration is the same.

Hence, the answer is the option (2).

Example 3: In the sixth period, the orbitals that are filled are :

1) (correct) 6s, 4f, 5d, 6p

2) 6s, 5d, 5f, 6p

3) 6s, 5f, 6d, 6p

4) 6s, 6p, 6d, 6f

Solution: Energy order of orbitals according to Aufbau principle-

The order of orbitals filling is 6s, 4f, 5d, 6p.

Therefore, the correct option is (1).

Example 4: Element "E" belongs to the period 4 and group 16 of the periodic table. The valence shell electron configuration of the element, which is just above "E" in the group is

1) (correct) 3s2,3p4
2) 3 d10,4 s2,4p4
3) 4 d10,5 s2,5p4
4) 2s2,2p4

Solution:
The element " E " will be Se (Selenium), it belongs to period 4 and group 16 of the periodic table.
Just above Se,S (sulfur) is present. The valence shell electronic configuration of Sulfur is 3 s2,3p4
Hence, the answer is the option (1).

Example 5: The electronic configuration of Pt (atomic number 78) is :
1) (correct) [Xe]4f145 d96 s1
2) [Kr]4f145 d10
3) [Xe]4f145 d10
4) [Xe]4f145 d86 s2

Solution:

The electronic configuration of Pt(78) is [Xe]4f145 d96 s1

Hence, the answer is the option (1).

Conclusion

All in all, the study of electronic configurations deepens one’s understanding of how atoms are built and how this shapes the chemical world. On this basis, we eventually explain the reactivity, bonding, as well as behaviours of different elements in the periodic table by understanding the distribution of electrons’ energy levels in the atomic structures. Pauli exclusion principle states that no two electrons present in an atom can have the same four quantum numbers and Hund’s rule for establishing the electron configuration to minimize energy is critical in the chemists’ attempts to predict the chemical properties of an element and its reactivity with other substances.