Atomic Orbital

Introduction

Atomic orbitals are the three-dimensional spaces that surround the nucleus and are most likely to contain an electron. The atomic orbitals have been combined to create molecular orbitals. They obtain orbitals in quantum theory, some of which are electron shells in the s, p, d, and f configurations. Although orbitals come in a variety of shapes and sizes, their square can be used to estimate their size or even shape. A total of two, six, ten, or fourteen electrons could fit in the s, p, d, and f subshells, respectively. The particular arrangement of electrons within orbitals in such an atom determines the majority of the chemical compositions of that atom. Depending upon the energy over its electrons, every orbital class seems to have a distinct form. The s orbital has a spherical geometry. The p orbital has the form of a dumbbell, as well as 3p orbitals, which vary in their arrangement across a 3-dimensional axis.

Image of  S,p,d atomic orbitals

Define Atomic Orbitals

Atomic orbitals are numerical values that provide additional details about the waveform of electrons that inevitably surround atom centers. In the fields of quantum systems and atomic theory, specific mathematical expressions are frequently employed to determine the likelihood of detecting an electron at even a specific area surrounding the nucleus of an atom. The term “atomic orbital” may also refer to the region above an atom’s nucleus where there is the greatest chance that a particular electron will become accessible. Several quantum numbers affect each atomic orbital’s characteristics:

Table of All Possible Atomic Orbitals, where the Value of ‘n’ Ranges from 0 to 5

What do you mean by Atomic Orbital Theory?

An atomic orbital is a statistical term that describes the location or even waveform behavior of such an electron in an atom in both atomic theory and quantum field theory. These electrons, each of which has a distinct spin quantum number s, can fit into any one of these orbitals up to a maximum of two. One such formula can be used to determine whether it is possible to find an electron inside the nucleus of any atom at any particular location.

Summary

Atomic orbitals seem to be the regions around the nucleus of an atom where electrons have often been observed at that particular time. This is a mathematical concept that characterizes the wave-like activity with 1-2 electrons in an atom. Electrons inhabit low-energy orbitals (near such nuclei) before electrons approach higher-energy orbitals. When there is an option of equal-energy orbitals, then occupy the orbitals freely as feasible. That filling of orbitals on its own is termed Hund’s law when applicable. Atomic orbitals are typically denoted by a series of digits as well as letters representing unique features of such electrons linked only with orbitals, including 1s, 2p, 3d, as well as 4f. Primary quantum numbers are values that further indicate levels of energy.

Frequently Asked Questions (FAQs)

1. Is it possible to have an orbital without an electron?

Ans. An orbital’s characteristics are more like the electron residing inside it. This is standard procedure, however irrational this could appear, to refer to ‘Empty orbitals.’ The characteristics of unoccupied orbitals are the same as those computed for electrons within them.

2. What is perhaps the greatest number of orbitals possible?

Ans. The values n=3 & l=1 indicate that it has been a 3p-orbital, however, the number \(f(m_{l}=0)\) indicates that it is indeed a \(3p_{z}\) in origin. As a result, the specified quantum number can only identify one orbital, namely 3p_z.

3. How do electrons fill orbitals?

Ans. According to the Aufbau principle, electrons first occupy lower-energy atomic orbitals before moving onto the higher ones. Based on this method, we may forecast the electronic structure of atoms and ions.

Aufbau Principle

Introduction

Aufbau is a German word that means “building up.” Like a construction build-up from the ground up. Atoms are also filled with electrons in this manner. An atom has orbitals that are arranged in increasing energy level order. According to the Aufbau principle, electrons are filled in the order of increasing energy of the atomic orbitals. That is from the bottom to the top. This principle aids in the electronic configuration of atoms as well as the placement of electrons in orbitals. In all atoms, the orbital is always the first orbital to be filled with electrons. After filling this orbital, electrons are filled in orbitals further away.

Explain Aufbau Principle

Niels Bohr, a Danish physicist developed the principle. According to this principle, the increasing order of energy levels of atoms causes the filling of electrons in an atom. They are entering a perfect order that corresponds to the energy level of orbitals.  We can predict the electron configurations of atoms or ions by using this rule.

The Madelung rule or rule is also related to this rule. According to this rule, the filling of electrons in an atom occurs as the value of n+l increases. That is, the electrons are filled to a lower-valued orbital. Where n represents the principal quantum number value, and l represents the angular momentum quantum number value. This is known as the Madelung rule or the diagonal rule.

Electrons getting filled up according to Aufbau principle.

Some features of the Aufbau Principle

  1. Electrons are assigned to the subshell with the lowest energetically available energy.
  2. An orbital can only hold two electrons.
  3. If two or more energetically equivalent orbitals (e.g., p, d, etc.) are available, electrons should be spread out before being paired up (Hund’s rule).

Some Exceptions 

Some elements exhibit exceptional behaviour in terms of the Aufbau principle. They are chromium and copper, respectively. According to the Aufbau principle, the electronic configuration of chromium is \(\left[ {Ar} \right]3{d^4}4{s^2}\). However, chromium’s electronic configuration is \(\left[ {Ar} \right]3{d^5}4{s^1}\). And this is because chromium achieves stability by having a half-filled orbital. Elements require a filled state at all times. A fully-filled orbital is always more stable. Even though a half-filled orbital has partial stability.

Copper’s electronic configuration is \(\left[ {Ar} \right]{\rm{ }}3{d^{10}}4{s^1}\) rather than \(\left[ {Ar} \right]{\rm{ }}3{d^9}4{s^2}\). This is due to the presence of a fully-filled d-orbital configuration, which provides additional stability.

Summary

An electronic configuration is present for all elements to locate electrons in orbitals. As a result, the chemical properties of elements can be explained. When combined with other rules, this can result in a proper electronic configuration. According to Aufbau’s principle, the filling of electrons in an atomic orbital occurs in the order of increasing energy of atomic orbitals. The elements chromium and copper are exceptions to this rule. Because they achieve a half-filled and fully-filled atomic orbital, these elements can be more stable.

Frequently Asked Questions

1. Define Hund’s rule of maximum multiplicity

For an orbital of the same sub-shell, the filling of electrons takes place in a way that all the electrons are singly occupied before pairing occurs. The pairing of electrons takes place only when all the subshells are singly occupied.

2. What do you understand by Pauli’s exclusion principle?

All the quantum number values are distinct for each electron present in an atom. This principle states that no two electrons in an atom can have an equal set of all the quantum number values. And thereby we can easily locate all the electrons in an atom.

3. What is the principal quantum number?

The number that deals with the energy and size of orbitals are a principal quantum number. It will explain how far an electron is from the nucleus. For example, the electronic configuration of Helium is \(1{s^2}\) so the principal quantum number is 1.