Atomic structure

Atomic Structure

Here you will learn about different atomic models that completely describe the structure of the atom, these are Dalton’s atomic theory, J.J. Thomson, Ruther Ford, Bohr, and the Quantum mechanical model of the atom.

Atomic structure

The term "atomic structure" describes the structure of an atom, which has a nucleus (center) that contains both protons (positively charged) and neutrons (neutral). The center of the nucleus is circled by negatively charged electrons.

Democritus, who initially claimed that matter is made up of atoms, is credited with establishing the history of atomic structure and quantum mechanics. An excellent understanding of the complete class of chemical processes, bonds, and their physical characteristics can be gained from studying atom structure. In the 1800s, John Dalton put forth the initial scientific theory of atomic structure.

Atom:

Extremely small particles of matter are called atoms.

Nucleus:

The central part of an atom is called a nucleus. It contains protons and neutrons.

Electrons:

Electrons are negatively charged atomic particles that revolve around the nucleus of an atom. Electrons are discovered by Thomson.

Protons:

Protons are positively charged atomic particles that are present inside the nucleus of the atom.

Neutrons:

These are particles that have no charge, these are neutral particles present in the nucleus of an atom.

Atom

Atomic Models

John Dalton’s theory of an atom

John Dalton, an English physicist, and chemist proposed the atomic hypothesis in 1808 as a scientific theory about the composition of matter. It claimed that tiny, indivisible particles called "atoms" make up all substances.

According to Dalton's atomic theory, atoms, which are indestructible and indivisible fundamental building blocks, make up all substances. Unlike other elements, which had atoms of different sizes and masses, an element's atoms all had the same size and mass.

Postulates:

Atoms are the smallest, undivided building blocks of all substances.

A particular element's atoms are all the same mass, size, and other characteristics. Nevertheless, the characteristics and mass of atoms from various elements differ.

Atoms are eternal and cannot be generated or destroyed. Atoms also cannot be separated into smaller components.

Compounds can be created by combining atoms of various elements in particular whole-number ratios.

In chemical changes, atoms can be bonded, detached, or modified.

John Dalton Model 

Limitations:

Dalton's atomic theory claimed that atoms were indestructible, hence it did not take into consideration subatomic particles. This assumption was refuted by the discovery of subatomic particles like protons, electrons, and neutrons.

Isotopes are not taken into account. According to Dalton's atomic theory, the masses and densities of every atom in an element are the same. However, the atomic masses of certain element isotopes vary (For example, hydrogen, deuterium, and tritium).

Isobars are not taken into account. According to this idea, the masses of the atoms in two distinct elements must be different. But two distinct elements have the same mass number. These atoms are known as isobars (Example: 40Ar and 40Ca).

Compounds can be formed by the combination of elements in complex, not whole-number ratios. There are some complex organic compounds that don't have straightforward atom-to-atom ratios. Example: sucrose or sugar (C11H22O11).

Allotropes are not taken into account by the theory. Dalton's atomic theory is unable to account for the discrepancies between the properties of diamond and graphite, both of which are made up entirely of carbon.

Advantages:

Dalton's atomic theory does not violate the "laws of multiple proportions, conservation of mass, or constant proportions".

A foundation for distinguishing between elements and compounds is provided by the theory.

J.J. Thomson atomic model

William Thomson put forth the Thomson atomic model in 1900. This model provided a theoretical explanation of the description of an atom's interior structure. Sir Joseph Thomson, who had earlier made the discovery of the electron, backed it wholeheartedly.

J.J. Thomson found a negatively charged particle during a cathode ray tube experiment. In 1897, this experiment was conducted. A vacuum tube is a cathode ray tube. The electron was the name given to the negative particle.

Thomson believed that each atom is composed of millions of electrons and assumed that an electron is 2,000 times lighter than a proton. He took into account atoms surrounded by a cloud that had both positive and negative charges in his concept of the atomic structure. He and Rutherford also performed an X-ray demonstration of the ionization of air. They were the ones who initially showed it. The atom in Thomson's model resembles a plum pudding.

William excluded a nucleus, protons, and neutrons from his model.

Postulates:

A positively charged sphere with contained electrons makes up an atom.

Because the magnitudes of the positive and negative charges are equal, an atom as a whole is electrically neutral.

A watermelon analogy is made for the Thomson atomic model. Where he thought:

As negatively charged particles, watermelon seeds

The watermelon's red portion is positively charged.

 

J. J. Thomson Model of Atom 

Limitations:

Because his atomic model did not adequately describe how a positive charge retains the negatively charged electrons in an atom, it was unable to explain why an atom is stable. As a result, this idea was also unable to explain where the atom's nucleus is located.

The scattering of alpha particles by thin metal foils was not adequately explained by Thomson's model.

There are no experimental facts to support it.