Drawbacks of Rutherford’s Atomic Model
When asked about the most basic and fundamental unit that exists, the name that comes to mind is an atom. Atom is the root of the formation of matter, that is, every matter is made up of atoms, and it is the building block of matter. In chemistry, the structure and the features of an atom are discussed along with the history attached to it. The discovery of an atom and its structure was not so simple and was explained with a lot of experimentation and failures. The discovery of the atom led to explanations and questions regarding the structure of an atom, one such structure was introduced by the scientist Rutherford known as the “Rutherford’s model of an atom”. Let’s learn in more detail,
Rutherford’s Atomic Model
Many scientists came up with different ideas and explanations of the structure of an atom. The most classical model was introduced by the scientist named Ernest Rutherford. Rutherford’s model later was said to be not the accurate version, however, the model did give a brief introduction to what and how the atom is formed. Rutherford explained that an atom is mainly made up of Electrons, Protons, and neutrons, and they are arranged in the atom in a fixed manner.
According to Rutherford’s model of an Atom, an atom is made up of mostly empty space and there exist electrons with spaces revolving around the nucleus in their fixed paths. The nucleus is positively charged due to the presence of protons (the positive charge), apart from the protons, neutrons (no charge on them) are also present inside the nucleus.
It can also be said that the electrons were embedded uniformly around the positively charged nucleus, and the force between was the positive and the negatives charges is what keeps an atom in place and intact.
Rutherford’s Alpha- Scattering experiment
The British physicist “Rutherford” conducted an experiment by bombarding alpha particles on a thin sheet made up of gold. As soon as the particles hit the gold foil, they gained certain trajectories and the trajectories were studied by Rutherford. The gold sheet being extremely thin (around 100nm thickness) when met with the high energy beamed alpha particles, the sheet deflected the particles and were collided on the fluorescent Zinc sulfate screen that was placed around the foil. Observing this, Rutherford made certain observations.
Observations
- A very major area of the alpha particles did not deflect and simply passed through the foil indicating that the atom has mostly empty space and hence, nothing to deflect the particles.
- Since alpha particles are positively charged, they are expected to get deflected by the positive charges, but some alpha particles were deflected by a very small angle indicating that the positive charge inside an atom is not uniformly distributed.
- Hence, it was concluded that the positive charge is concentrated in a very small volume inside the atom.
- There were very few particles that were deflected back and even fewer that deflected 180° concluding that the space taken by the positive charge inside the atom is very, very small as compared to the actual size of the atom.
Points taken from Rutherford’s Atomic Model
- Most of the atom is nothing but empty spaces.
- Most of the mass present inside the atom was concentrated in a small area at the Centre, called the nucleus.
- The electrons revolve at very high speeds around the nucleus in their own fixed paths known as orbits.
- The strong electrostatic force of attraction between the positive and negative charges is responsible for the stable model of an atom.
Drawbacks of Rutherford’s model of an Atom
The model of the atom proposed by Rutherford is still known as the classical model and was very much accepted at that time, however, later on, it was revealed that there were certain aspects that this model was not able to answer, hence, certain drawbacks of Rutherford’s model of an atom were introduced, they were as following:
- According to Maxwell, electrons should emit electromagnetic radiations as any accelerated charged particle has the tendency of emitting electromagnetic radiation. Rutherford also stated that the electrons do revolve around the nucleus in their orbits. Hence, due to the kinetic motion of the electrons, the radiations shall lead to the shrinking of the electrons in less than 10 seconds as the atom will keep on losing energy. Therefore, when Rutherford’s model was mixed with Maxwell’s theory, it was realized that the model is flawed.
- Rutherford did explain the revolving of electrons around the nucleus, however, the physicist did not mention how the electrons were placed inside, which ended up making Rutherford’s model an incomplete model of the atom.
Conceptual Questions
Question 1: Why gold was used as a thin sheet in Rutherford’s alpha scattering experiment?
Answer:
Since Gold has the best malleable property as a conductor, it could easily be formed into the thinnest sheet in order to observe an atom and its structure.
Question 2: What is the major drawback of Rutherford’s model of an atom?
Answer:
According to Maxwell, any accelerated charged particle in motion emits electromagnetic radiation and this in Rutherford’s model could lead to the collapsing of the atom as the atom will constantly lose energy due to the accelerated charged electrons.
Question 3: Explain the particle used in the experiment done by Rutherford.
Answer:
The particle used was Alpha particles, denoted as “α” and alpha particles have 4 units of mass and 2 units of positive charge present on them. They are emitted from materials like Radium that are radioactive in nature. They can easily penetrate through objects, and since, atom has concentrated positive charge, they were able to deflect.
Question 4: Most of the atom is empty spaces. How was this statement concluded?
Answer:
When alpha particles were bombarded on the gold sheet, it was observed that most of the alpha particles went straight without any kind of deflection. This proved that most of the space in an atom is empty.
Question 5: What was one accuracy in Rutherford’s model of an atom?
Answer:
The accuracy in Rutherford’s model was regarding the position of the protons and facts about nucleus. Rutherford concluded that the protons are concentrated in a very small volume in the atom along with the neutrons and this small volume is known a nucleus.
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