Daltons Atomic Theory Assignment Help




Atomic theory:

An atomic theory is that theory that described the complete structure of the atom.  Scientist starts to discover atomic theory from the early of eighteen century. And now, we have a well discovered atomic theory that gives the complete explanation of the atomic structure. The various atomic theories are J.J. Thomson theory, Rutherford theory, and Bohr’s model. But the discovered theory that explains the complete structure of an atom is the Bohr’s model.

Atomic Theory: J.j. Thomson Theory

After the discovery of the electron and proton as subatomic particles J.J. Thomson had started to discover atomic theory that gives complete explanation of atomic structure. According to the Thomson protons are embed in the atoms like a water melon and electrons are present in atoms to make the atom electrically neutral. This discovered atomic theory was not able to explain the atomic structure properly.

Atomic Theory: Rutherford’s Atomic Theory

Rutherford’s discovered atomic theory to explain the structure of atom.  For that he bombarded the alpha particle on the gold plate, from his observations he discovered an atomic theory.

  • Atoms are electrically neutral in nature

  • A large heavy mass is present in the centre of an atom that have protons and neutral subatomic particles.

  • Electrons are revolves around the nucleus in the fixed circular path known as orbit.

This discovered atomic theory was largely accepted and gives a complete explanation of structure of an atom.

Atomic Theory: Bohr, S Model

 Bohr’s discovered atomic theory is an important theory that completely explains the structure of an atom. He proposed this model after the discovery of neutron, neutral subatomic particles described by the Rutherford.

The postulates of Bohr’s discovered atomic models are

  • A heavily mass positively charged nucleus is present in the centre of an atom is known as nucleus. Nucleus has both protons and neutron. The charge of the nucleus is due to the protons present in the nucleus as neutrons are the electrically neutral. But they contribute towards the mass of atom as their mass is equal to the mass of the proton.

  • Electrons are revolves around the nucleus in a fixed particular path known as orbit. The no. of electrons in an atom is equal to the number of proton. So, that atom remains electrically neutral.

  • When an electron jumps from the lower orbit to the higher orbit, it absorbs energy, while when it comes in to the lower orbit from the higher orbit it loses energy in the form of radiation.

Dalton's Atomic Theory:-

Introduction to Dalton's Atomic Theory:

    Dalton's Atomic theory was proposed by John Dalton an English chemist, physicist, a very well known meteorologist and a great philosopher. He is known for his works like Dalton's Atomic theory, Dalton's laws of partial pressures, Law of multiple proportions, research work on colour blindness etc.... His first publication was meteorological observations and essays which was published in 1793.His laws and works are applied in various branches of chemistry both industrial and research fields.

Main Points of Dalton's Atomic Theory

1. The smallest particle of the matter, which involves in chemical bond is known as atom.

2. Atom is an indivisible according to Dalton

3. All the atoms of the same element are identical

4. Atoms of one element can combine with atoms of other element in a chemical reaction and gives the compound in which relatively the same numbers of the reacting atoms are present.

5. Atoms of one element are different from the other element and they can be differentiated by their respective atomic weights which are very specific for an atom.

Drawbacks of Dalton's Atomic Theory.

   In Dalton's Atomic theory the atom is said to be indivisible but the discharge tube experiments explain that the atom is divisible. This is a very big drawback to the Dalton's atomic theory. Dalton's atomic theory could not explain the existence of the allotropes. Existence of different forms being made of same atoms could not be explained by this theory. As said in the Dalton's Atomic theory all the Atoms are similar in the properties was proved wrong after enlightened with the knowledge of the isomers which are made up of same atoms but have different atomic weights.

Another drawback is that the atom can be further divided into Electrons, Protons and Neutrons. The other particles like Mesons, Anti electrons, etc... are known as sub atomic particles, they are formed due to the stress and strain of the nucleus ,i.e. inter conversion of nucleus. And the atoms not only combine in simple ratios they can combine complexly to form complex organic molecules.

Merits of Dalton's Atomic Theory

Even though it has many drawbacks but still it is credited to explain the chemical combinations, which lays the basis for chemical combination laws. Several chemical reactions are simplified by the scientists using these laws. Dalton’s theory is the first theory to explain in depth about atom, which is the reacting particle in the element and the formation of molecules by the atoms was explained correctly and it follows the conservation rules.


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