What is an Atom?

An atom is the smallest unit of an element (substances or matter) divided into charged particles (electron, proton, neutron). The smallest unit or basic building block of matter also contains the same characteristics and properties of constituent elements in chemistry or physics. Therefore, atoms are very small in size and their radius is measured in nanometers.

What is an atom and atomic structure?

Many atoms (hydrogen, oxygen, nitrogen, etc) are not capable of independent existence. However, atoms of noble gases (helium, neon, argon, etc) are capable of existing independently.

We have learned from Dalton’s atomic theory that atoms are the fundamental building blocks of matter. Daltons assumed that an atom of an element is indivisible or does not contain constituent particles.

Atomic Structure

Experimental evidence suggests that atoms are not the smallest particles because some other particles smaller than atoms are also present. These are called sub-atomic particles (electron, proton, and neutron).

Many scientists proposed various atomic theories and models to know the arrangement of such particles within the atoms. These may include:

  • Thomson’s atomic model (given by J.J. Thomson)
  • Rutherford’s atomic model (given by the British scientist Ernest Rutherford)
  • Bohr model of an atom (given by the Danish physicist Neil Bohr)
  • The quantum atomic model (given by Austrian physicist Erwin Schrödinger)
Planck's quantum theory or equation presented by Max Planck quanta or photon energy and Black body radiation

Planck’s Quantum Theory

What is Planck's Quantum Theory? Planck's quantum theory was presented by Max Planck on December 14, 1900. According to Planck's quantum theory, an atom or...
Electron arrangement structure of nitrogen atom


What is an Electron Particle? Electron, the lightest subatomic or elementary particle of atom carries a negative charge, −1.602176634 × 10−19 coulomb or −4.8 ×...
Set of the quantum numbers to define orbital diagram shapes

Quantum Number

What are Quantum Numbers? Quantum numbers such as principal, azimuthal, magnetic, and spin quantum number are the identification number of an electron in an atom....
relation between quantum numbers- for atomic theory questions and answers (quiz)

Atomic Theory Questions

Atomic Theory Questions and Answers Atomic theory questions or quizzes set in online learning chemistry for school college students contain 9 questions and answers. These...
de Broglie wavelengths, frequency and energy relation for light photon or electron

de Broglie Relation

de Broglie Hypothesis de Broglie wavelength relation pointed out that just like photons of light, electron have both particle and wave properties of matter. It...
bohr model of hydrogen energy levels

Bohr Model

Bohr Model of Hydrogen Atom Bohr Model of hydrogen atom was adopted by Neils Bohr in 1913 for the explanation of the Rutherford model and the...
Subatomic elementary particles like electron, proton and neutron of an atom

Elementary Particles

What are Elementary Particles? Elementary particles or subatomic particles like electrons, protons, and neutrons in physics or chemistry were discovered by Scientists Thomson, Golstine, and...
Ernest Rutherford model or nuclear planetary model of atom in chemistry or physics by gold foil experiment

Rutherford Model

Rutherford Model of an Atom Rutherford model or nuclear planetary model of an atom in chemistry or physics describes by New Zealand-born physicist Ernest Rutherford...
Electron or electronic configuration of elements in periodic table, group wise general formula for s, p-block and 3d series

Electron Configuration

Electronic Configuration of Elements in Periodic Table Electronic configuration or general electron configuration or electronic structure of atoms or ions is the arrangement of orbital...