Atomic Scale

The structure of an atom is made up of a nucleus (the center), protons (positively charged), and neutrons (neutral). Electrons, which are negatively charged particles, form a ring around the nucleus’s center.

Atomic structure and quantum mechanics can be traced back to Democritus, who was the first to propose that matter is made up of atoms. Atom structure research reveals a lot of knowledge on chemical processes, bonds, and their physical properties. John Dalton proposed the first scientific theory of atomic structure in the 1800s.

What exactly is an atomic structure?

The atomic structure of an element refers to the composition of its nucleus and the arrangement of electrons around it. The basic atomic structure of matter is made up of protons, electrons, and neutrons.

Protons and neutrons make up the nucleus of an atom, which is surrounded by electrons. The total number of protons in an element’s nucleus is described by its atomic number.

Protons and electrons are in equal numbers in neutral atoms. Atoms, on the other hand, can receive or lose electrons to strengthen their stability, resulting in an ion.

Because various elements contain different numbers of protons and electrons, their atomic structures differ. This is why various components have varied characteristics.

Atomic Models 

Many scientists attempted to describe the structure of the atom using atomic models in the 18th and 19th centuries. Each of these models had advantages and disadvantages, and they were important in the creation of the present atomic model. Scientists including John Dalton, J.J. Thomson, Ernest Rutherford, and Niels Bohr made significant contributions to the discipline. This section delves into their theories about atomic structure.

Dalton Atomic Theory

According to English chemist John Dalton, all matter is made up of indivisible and indestructible atoms. He further argued that while all atoms of the same element are the same size and mass, atoms of different elements vary in size and mass.

Chemical reactions, according to Dalton’s atomic theory, involve the rearrangement of atoms to produce products. The atomic structure, according to Dalton’s postulates, was made up of atoms, the smallest particles responsible for chemical reactions.

The following are his theory’s postulates:

1.Atoms are the building blocks of all matter.

2.Atoms are unbreakable.

3 There is just one sort of atom in each element.

4.Each atom has a fixed mass that varies depending on the element.

5 During a chemical reaction, atoms rearrange themselves.

6.Atoms cannot be generated or destroyed, but they can be changed into various forms.

Dalton’s atomic theory successfully explained chemical laws such as the Law of Conservation of Mass, the Law of Constant Properties, the Law of Multiple Proportions, and the Law of Reciprocal Proportions.

Drawbacks of Dalton’s Atomic Theory

1.The occurrence of isotopes was not explained by the idea.

2.Nothing concerning the atom’s structure was adequately explained.

3.Scientists later identified particles inside the atom, proving that atoms are divisible.

4.The discovery of subatomic particles (particles inside atoms) led to a better understanding of chemical species. 

Thomson Atomic Model  

Sir Joseph John Thomson, an English chemist, offered his model for determining atomic structure in the early 1900s.

He was later awarded the Nobel Prize for discovering “electrons.” His study relies on a technique known as cathode ray experimentation. The experiment’s working structure is as follows:

Play around with Cathode Rays.

It has a glass tube with two holes, one for the vacuum pump and one for the gas input.

The vacuum pump’s duty is to maintain a “partial vacuum” in the glass chamber. Electrodes (cathode and anode) are connected to a high voltage power supply within the glass tube.

Observations

1.When a high voltage power supply was turned on, rays emerged from the cathode and traveled towards the anode. The ‘Fluorescent dots’ on the ZnS screen utilized this. “Cathode Rays” were the name given to these rays.

2.The cathode rays are bent towards the positive electrode when an external electric field is introduced, but they move in a straight path when there is no electric field.

3.Rotor Blades appear to rotate when placed in the path of cathode rays. 

4.This demonstrates that cathode rays are composed of particles of a specific mass and so have energy. 

5.Thompson determined that cathode rays are made up of negatively charged particles known as “electrons” based on all of the evidence.

6.Thomson discovered the charge to mass ratio (e/m) of electrons by applying an electric and magnetic field to cathode rays (electrons).

Mullikin discovered the charge of the electron from this ratio via an oil drop experiment. [e– has a charge of 

1.6 × 10^-16 C and a mass of 9.1093 × 10^-31 kg].

Thomson defined the atomic structure as a positively charged sphere with negatively charged electrons embedded in it, based on the results of his cathode ray experiment.

The “plum pudding model” is so named because it can be imagined as a plum pudding dish with the pudding representing the positively charged atom and the plum pieces representing the electrons.

The positive and negative charges in atoms were of equal magnitude according to Thomson’s atomic structure.

Conclusion

We conclude that an atom is the smallest unit of substance that can be divided while retaining the properties of an element. The word comes from the Greek atomos, which means “indivisible,” and the atom was thought to be indivisible until electrons and the nucleus were found in the early twentieth century.