Atomic Structure in Chemistry and an Atom Definition

In this post, We shall learn about Atomic Structure in Chemistry and an Atom Definition. We all know it is the most important part in Chemistry and also in Government job exam 2 or 3 questions come from this topic. Let’s see the contents table what we are going to cover today.

The Concept of Atoms and Dalton Atomism

In 1808, English scientist Sir John Dalton published a definitive scientific theory about the structure of matter. This theory is known as Dalton’s Atomism. The basics of atomism are (An Atomic Structure / Definition) :
(1) All substances are composed of numerous very small indivisible nonrated particles The smallest particle in the substance is the atom.
(2) Atoms cannot be broken down, created or destroyed by chemical processes. Atoms are indestructible and indivisible.
(3) Atoms of the same basic substance are identical in weight and religion.
(4) Atoms of different basic substances are different in weight and religion.
(5) Atoms of various elemental substances produce composite substances in simple proportions of integers. For example – 1: 1, 1: 2, 2: 3 etc.
(6) Atoms of the same basic substance produce multiple compounds, joining them in proportion to one or more. Such as – NO, NO2, H2O, H2O2 ….. etc.

Atomic structure

Atoms of matter are usually composed of three main particles – electron, proton and neutron. Only ordinary hydrogen atoms do not have neutrons. Each atom is divided into two parts. Namely –
 (i) Positive electrons or nucleus of atoms
(ii) electrons outside the nucleus.
Atomic structure

[i] Positive Electrons or Nuclei of Atoms

Scientist Rutherford hypothesized the first nucleus by examining the distortion of alpha particles in gold. After analyzing the results of the experiment, Rutherford decided that in a small space in the centre of the atom, almost the entire mass and positive mass of the atom were stored. The centre of the atom has a positively charged, heavy and very small part called the Atomic Nucleus.

 [ii] Electrons Outside the Nucleus

Proton and electrons are in equal numbers in the electrons. The electrons are arranged in different cells in the rest of the atom outside the nucleus. This arrangement of electrons is called the Electron-Mass.
Atomic Structure Diagram
Atomic Structure Diagram

Structure of Nucleus

[1] The nucleus is much smaller than the whole atom. If you imagine a sphere in an atom, its radius is about 10-10 meters, where the radius of the nucleus is about 10-14; That is, about 1 / 1000.00% of the radius of the atom.
[2] After the discovery of neutron particles, it is known that the nucleus of the atom is made up of protons and neutrons. There are no electrons in the nucleus.
[3] The number of protons and neutrons in the nucleus varies with respect to the element. However, there is only one proton in the hydrogen nucleus, no neutrons.
[4] The basic particles (protons and neutrons) of the nucleus are commonly called nucleons.
[5] The total mass of a proton and a neutron is the mass of that nucleus. Again, since the mass of an electron is less than the mass of a proton or a neutron, the mass of the nucleus is actually equal to the mass of the entire atom.
[6] Although the mass of the nucleus is small, the density of the nucleus is very high because its volume is very small.
[7] The total positive loss of protons in the nucleus is that of the nucleus.
[8] The nucleus is the most stable part of an atom.

Nuclear Force

The protons and neutrons are tightly aligned in the nucleus of the atom. But homogeneous positively charged protons are in one place without mutating. It is assumed that mutual mutations occur between the proton and the neutron in the nucleus. This transformation results in the formation of a small force (short distance = 10-12 cm approx) between them. The name of this attraction ball is the nuclear ball. Under the influence of this attraction force, homogeneous proton particles and passive neutron particles can bind to the nucleus of the atom, and the nucleus stabilizes and stabilizes.
Nuclear Force
Nuclear Force

Nature of the Nuclear Ball

In 1935, the scientist Yukawa developed the Meson theory to determine the nature of the nucleus force. According to this theory, the respective entities of protons and neutrons are not permanent. Inside the nucleus, 273 times the mass of electron-massed electrons [π + and π-] within the proton-neutron, mutations are always converted into a neutron-π proton and proton-π neutron (neutron-proton + π- and proton + π- and proton). +) And the resulting intense attraction forces the proton and the neutron to bind together. Again, the proton-1 proton, or neutron, is the passive Mason particle responsible for binding the neutron. The existence of these Mason particles has been recognized in experiments in 1943.

Atomic Number and Mass Number


Atomic Number: – The total number of positive electrons located in the nucleus of an element’s atom, called the atomic number or an atomic number of that element.

Since the number of positive electrons in each proton is one unit; Therefore, the total number of protons in the nucleus of an atom is that atomic number. The atomic number is expressed by the letter ‘Z’.

Mass Number:- The total number of protons and neutrons located in the nucleus of an atom of an element called the mass of that element or atom. That is mass = proton number + number of neutrons. The mass is expressed with the letter ‘A’.

  • Relationship between mass numbers and atomic numbers: – If an atom of an element has a P-number of protons and an N-number of neutrons,
  • Atomic mass (A) = proton-number (P) + neutron-number (N)
  • Since, proton-number (P) = atomic-number (Z)
  • Therefore, the mass (A) = atomic-number (Z) + neutron-number (N) or Z = A – N
  • An atomic number of oxygen (Z) = 8 and mass-number (A) = 16; So oxygen is released by writing 8O16.
  • Atomic mass: – The mass of a carbon-12 (6 C12) atom is 12 times as large as any other mass of a C-12 atom in another element. That is
  • The atomic mass of element = mass of 1 atom of element / 1 / 12th of the mass of the C-12 atom.
  • Since the atomic mass of the two ratios is proportional, the atomic mass of the element is just a singular number.
Atomic Number and Mass Number

Distribution of Electrons in K, L, M, N Cells

[1] The electrons rotate around the nucleus in a circular and elliptical orbit of increasing radius, concentrated at a vacuum, but at different points. The nucleus or nucleus of the atom is located at any one of the focuses of the ellipse.

[2] Electrons can orbit the nucleus in a total of 7 specific orbitals. These orbits are called the main energy levels or quantum shells. During orbit, the electrons do not radiate any energy, their average energy is fixed. The number by which the quantum level is expressed is called the main quantum number (n). The value of n indicates the strength of the electron cell. According to the increasing distance from the nucleus, these orbits are K (n = 1), L (n = 2), M (n = 3), N (n = 4), O (n = 5), P (n = 6) and Q (n = 7) is called the orbit.

[3] The maximum number of electrons in each cell is fixed. This number is 2 x n2, where n is the main quantum number. n = 1, 2, 3, 4 …. etc. According to this rule, the maximum number of electrons can be 2 in K cell, 8 in L cell, 18 in M ​​cell, 32 in N cell.

[4] Regardless of the number of orbitals, there may never be more than 8 electrons in the outermost cell of an atom or the main energy source.

[5] In elemental cells that have 8 electrons in the outer cell (exception: 2 in the case of helium), the atoms are very stable. These elements are called inactive elements. For example – Neon, Argon, Xenon etc. These elements do not easily participate in chemical reactions.

Atom Nucleus Definition

The only element is known if the atomic number (or proton number) is known, but if its origin is parallel to that element, its nucleus cannot be identified. Because the number of protons in the nucleus of the atom of the same element is the same, the number of neutrons varies. That is, the mass of the element (proton + neutron) of the element is different. Therefore, to identify a nucleus, it is necessary to know the atomic number (Z) and mass (A) of that element. Atoms with a fixed atomic number (proton number) and mass (proton + neutron) are called nucleids. Such as: 1H1, 1H2, 1H3, 8O16, 8O17, 8O18, 17C35, 17C37, etc. Each is a nuclide.

Atom Nucleus Definition
Atom Nucleus Definition

Ion and cation

[ 1 ] Ion: – In general, any atom is in motion. That is, the number of protons in the atom = the number of electrons. When one or more electrons are taken from the outermost cell of an atom, that atom becomes an electron. This electron is called an ion . Ions are more stable than atoms.

[ 2 ] Cation: – one or more electrons from an atom, the atom is devoid of the positive taritgrastha kyatayane is turned. Such as – Na – e → Na +; Ca – 2e → Ca ++ etc.

[ 3 ] Anion: – If you receive any of the atoms of one or more electrons are negative taritgrastha ayanayana is turned. E.g., Cl + e → Cl-; S + 2e → S = et al.

[ 4 ] Travel Ionic example: – That is more than the sum of the atom, and testing may be taritgrastha yemana – ammonium (NH + 4) ion, nitrate (NO-3) ions and so on.


Isotopes are defined as different atoms of an element whose atomic numbers, ie, the number of protons, are different but the mass of the atoms, which is the number of neutrons in the nucleus, is different, they are called Isotopes.

Get More Information about Atomic Structure:

People also ask on Atomic Structure (Accroding to Google)

The Atomic Structure of Oxygen is 8 = neutrons, 8 = protons and 8 = electrons

John Dalton

Homi Bhabha

Johan August Arfwedson

Proton is a positive or positively charged particle.

The heaviest particle in the atom is the neutron and the lightest particle electron

The protein and neutron particles in the nucleus of an atom are called the central particles or nucleons.

The heaviest particle of any atom is a neutron .

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