Structure of the Atom - Notes, Topics, Formula, Books, FAQs

Have you ever thought about what the building blocks of everything we see around us in our daily life, from the air we breathe to the devices we use? The answer is atom. Understanding the structure of an atom helps us explain why substances behave the way they do, why chemical reactions occur, and how matter is organized at the microscopic level. In this chapter we understand the basic terms electrons, protons, neutrons, atomic number, mass number, isotopes, isobars, velocity, frequency, wavelength, wavenumber, orbitals, quantum numbers, etc.

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This Story also Contains

1. Important Topics Of Atomic Structure
2. Atomic Structure Overview:
3. Line spectrum of hydrogen
4. Quantum Numbers:
5. Atomic Structure Formulas:
6. How To Prepare The Atomic Structure
7. Previous Year Questions of Structure of Atom

Over the years, many scientists have come across and given the theories related to it. Dalton was the first to give postulates about the atoms that they were indivisible particles, but subsequent research proved that they have a complicated interior structure. Rutherford's gold foil experiment proposed the presence of a dense nucleus at the centre of the atom, whereas Thomson's model of "plum pudding" explains how electrons were contained in a positively charged sphere where positive and negative charges are disperse in a sphere. Rutherford's concept, however, was not able to explain how electrons do not collapse into the nucleus of the atom because of the opposite charges attraction The important topics of the structure of atoms class 11 are mentioned below in this article.

Important Topics Of Atomic Structure

Thomson Atomic Model:

Thomson had just discovered electrons in 1897, and this was actually the first model to try speaking about the internal configuration of atoms. This is commonly referred to as the "plum pudding model.". Thomson Atomic Model has many postulates that tell about the model.

Rutherford Atomic Model And Its Limitations:

The Rutherford Atomic Model, proposed by Ernest Rutherford, had several limitations like it could not explain the stability of atoms, it did not explain how electrons are arranged inside the atom, and many more.

The observations of the Rutherford Alpha scattering experiment are

1. Most of the part of the atom is empty and atom is spherical in shape.

2. Each atom consists of a small, heavy, positively charged portion located at the centre, known as nucleus.

3. All positive charges of an atom (i.e, protons) are present in the nucleus and electrons move around the nucleus in circular orbits.

4. Electrons and the nucleus are held together by electrostatic forces of attraction.

Limitations of Rutherford’s Model

1. Does not explain stability of the atom

2. Does not explain atomic spectra

3. Rutherford’s model did not describe why electrons do not fall into the nucleus or how they maintain specific energy states.

Electromagnetic Radiation:

Electromagnetic Radiation refers to the transmission of energy through oscillating electric and magnetic fields at the speed of light

Planck's Quantum Theory:

Planck's Quantum Theory states that energy can only be absorbed or emitted by atoms and molecules in discrete quantities which is called Quanta.

Photoelectric Effect:

The Photoelectric Effect is the emission of electrons from a material caused by electromagnetic radiation such as ultraviolet light.

Bohr's Model Of An Atom:

Bohr's Model Of An Atom is a model that describes an atom as a small, positively charged nucleus surrounded by negatively charged electrons in circular orbits.

Hydrogen Spectrum:

The Hydrogen Spectrum is the line spectrum emitted by a hydrogen atom when an excited hydrogen atom returns to its ground state.

De Broglie Relationship:

The De Broglie Relationship describes the relationship between a particle's wavelength and its momentum. It was introduced in 1924 by French physicist Louis de Broglie.

Quantum Numbers:

The Quantum Numbers are those which describe the location of an electron in an atom. They determine the properties of atomic orbital and electrons in that orbital.

Radial Nodes And Planar Nodes:

Radial Nodes and Planar Nodes are the regions in an orbit where the probability of finding an electron is zero. These are the spherical surfaces around the nucleus.

Frequency, Time Period, And Angular Frequency:

Frequency, Time Period, and Angular Frequency is the important topic of atomic structure. All these are parameters of periodic motion to define it completely. Frequency is defined as the number of vibrations per second or the number of complete oscillations per second. The time period is the time taken by a particular electron to revolve in a particular orbit.

Electronic Configuration:

Electronic Configuration describes the location of an electron around the nucleus of an atom. It is written by following the standard notation.

Stability Of Orbitals: Half-filled And Completely-filled:

Stability Of Orbitals: Half-filled And Completely-filled is the topic of atomic structure in which we study the stability of orbitals as Half-filled and completely-filled orbitals are more stable than other configurations because of symmetry and exchange energy.

Atomic Structure Overview:

In this chapter, the candidate will, first of all, know about the atomic theory proposed by Dalton in 1808 who regarded the atom as the indivisible particle of matter. At the end of the nineteenth century, it was proved that atoms are divisible and consist of three fundamental particles: Electrons, protons, and neutrons. Faraday then discovered electrons using a cathode ray discharge tube experiment. Neutrons were discovered by James Chadwick by bombarding a thin sheet of beryllium with alpha particles. Various atomic models were proposed to explain the structure of the atom. The aspirant will know about Thomson's plum-pudding model, Rutherford's atomic model, and Bohr's model of an atom.

Line spectrum of hydrogen

When an electric discharge is passed through gaseous hydrogen, the H2 molecules dissociate and the energetically excited hydrogen atoms produced emit electromagnetic radiation of discrete frequencies. These radiations are emitted because of electronic transitions upon de-excitation to different energy levels and on the basis of the final energy level of transition, the hydrogen spectrum consists of several series of lines named after their discoverers like Lyman series, Balmer Series, Paschen Series, Bracket Series, Pfund Series.

Line Spectrum of Hydrogen-like atoms

$\frac{1}{\lambda }=R{Z}^2(\frac{1}{n_1^2}-\frac{1}{n_2^2})$
Where $R$ is called Rydberg constant, $R=109677{\mathrm{cm}}^{-1},Z$ is atomic number
$n_1=$ final orbit occupied after de-excitation $=1,2,3\dots$
${\mathrm{n}}_2=$ initial orbit occupied before de-excitation

Lyman Series spectrum:

Transition of electrons from higher orbits to $n=1$ result in the Lyman Series

$n_1=1\text{ and }{n}_2=2,3,4\dots$

For the H atom, this lies in the Ultraviolet region. For elements with higher $Z$, the Balmer lines lie in the Ultraviolet region

Balmer Series Spectrum:

Transition of electrons from higher orbits to $n=2$ results in the Balmer Series

Where $n_1=2$ and $n_2=3,4,5,6\dots$
For the H atom, this generally lies in the visible region.

Paschen, Bracket, and Pfund Series spectrums:

Transition of electrons from higher orbits to $n=3,4$ and 5 respectively, result in the Paschen, Bracket, and the Pfund Series

These lines lie in the Infrared Region for the H atom.