Atomic Structure – Theories of Dalton Atomic Theory, J.J Thomson Model, Bohr’s Atomic Model and Rutherford Model

Atomic Structure

Atomic Structure – Theories:

• The atomic structure of an element is determined by the number of protons in the nucleus. The number of protons in an element’s nucleus determines how strong the atom’s nucleus is held together (termed “atomic number”). The number of protons also determines what element the atom is. For example, an atom with six protons in its nucleus is oxygen (O), while an atom with eight protons in its nucleus is neon (Ne).
• The number of neutrons in an atom’s nucleus can vary, and this affects the atom’s mass. For example, an atom of oxygen with eight protons and eight neutrons is slightly heavier than an atom of oxygen with eight protons and six neutrons.
• An atom’s electrons orbit the nucleus in shells. The number of electrons in an atom’s outermost shell determines how reactive that atom is. For example, an atom with two electrons in its outermost shell is less reactive than an atom with eight electrons in its outermost shell.

Dalton Atomic Theory

The Dalton Atomic Theory is a model that explains the nature of atoms. It was developed by John Dalton in the early 1800s. The theory states that atoms are the smallest particle of an element that has the chemical properties of that element. Atoms are made up of protons, neutrons, and electrons. The number of protons in an atom determines the element’s atomic number. The number of neutrons in an atom determines the atom’s mass number. The number of electrons in an atom determines the atom’s charge.

Postulates of Dalton Atomic Theory

• The atom is the smallest particle of an element that has the chemical properties of that element.
• All atoms of a given element are identical.
• Atoms of different elements are different.
• The atoms of a given element are held together by chemical forces.
• The atoms of different elements are held together by chemical forces.

Drawback of Dalton Atomic Theory

The main drawback of Dalton’s atomic theory is that it does not explain the nature of the forces that hold atoms together. Dalton believed that atoms were held together by forces that were similar to the forces that held magnets together. However, he was not able to explain how these forces worked.

J.J Thomson Model

The electron is a subatomic particle with a negative electric charge. It is one of the fundamental particles that make up atoms. The electron was first discovered by J.J. Thomson in 1897. Thomson used a cathode ray tube to bombard a piece of metal with a beam of electrons. He observed that the metal emitted a beam of light when the electrons hit it. Thomson also found that the electrons had a negative charge.

Bohr’s Atomic Model

The Bohr model is a model of the atom that was developed by Niels Bohr. The model is a representation of the atom as a small, positively charged nucleus surrounded by electrons. The electrons orbit the nucleus in fixed shells. The Bohr model is a simple model that explains the emission and absorption of light by atoms.

Demerits of Bohr’s Model

1. Bohr’s model is too simplistic.
2. The model does not account for the behavior of matter at very high temperatures.

Cathode Ray Tube Experiment

In this experiment, you will use a cathode ray tube to measure the velocity of an electron.

• Cathode ray tubes were once common in televisions and other electronic devices. They are now mostly obsolete, but they can still be found in some old equipment.
• A cathode ray tube is a glass tube with a cathode at one end and an anode at the other. Electrons are emitted from the cathode and travel through the tube. When they reach the anode, they are accelerated by the electric field and strike a phosphor coating on the inside of the tube. This causes the phosphor to emit light, which is detected by a sensor.
• In this experiment, you will use a cathode ray tube to measure the velocity of an electron. You will first measure the velocity of an electron in a vacuum. You will then measure the velocity of an electron in a gas.
• The velocity of an electron in a vacuum is constant, regardless of the gas in the tube. The velocity of an electron in a gas is affected by the gas in the tube.

Properties of Cathode Rays

• Cathode rays are negatively charged particles that are emitted from the cathode of a vacuum tube.
• Cathode rays are attracted to the anode of a vacuum tube.
• Cathode rays are able to penetrate thin pieces of metal.
• Cathode rays are able to cause phosphorescence in certain materials.
• Cathode rays are able to produce an electric current in a vacuum tube.

Rutherford Model

The Rutherford model is a model of the atom that was developed by Ernest Rutherford.

The Rutherford model is a model of the atom that was developed by Ernest Rutherford. In this model, the atom is represented as a small, positively charged nucleus surrounded by electrons. The electrons are located in a region around the nucleus called the electron cloud. The Rutherford model was developed in 1911 and is still used today.

Construction of Alpha Scattering Experiment

• The Alpha Scattering Experiment is a device used to measure the scattering of alpha particles by a sample.
• The experiment consists of a detector and a sample. The detector is used to measure the scattering of alpha particles by the sample. The sample is a small piece of material that is used to scatter the alpha particles.
• The experiment is used to measure the scattering of alpha particles by a variety of materials. This information can be used to determine the structure of the material.

Alpha Scattering Experiment

• The Alpha Scattering Experiment was an experiment on the Apollo 11 mission to measure the lunar soil’s alpha radiation.
• The University of Chicago designed and built the experiment, which consisted of a stack of six detectors. The detectors were placed in the shadow of the Apollo 11 lander, and measured the alpha radiation from the lunar soil.
• The experiment found that the lunar soil had a much higher alpha radiation level than expected. This may have been due to the higher concentration of uranium on the moon.

Subatomic Particle of Atoms

The atom is the smallest particle of an element that has the chemical properties of that element. It is made up of protons, neutrons, and electrons.

Neutrons

Neutrons are uncharged particles found in the nucleus of an atom.

Electrons, Protons, and Neutrons

• The atom is the smallest particle of an element that has the chemical properties of that element.
• The atom consists of a nucleus and electrons.
• The nucleus contains protons and neutrons.
• The number of protons in an atom’s nucleus determines what element it is.
• The number of neutrons in an atom’s nucleus determines the isotope of that element.
• The number of electrons in an atom is equal to the number of protons in the nucleus.

Construction of Alpha Scattering Experiment:

• The alpha scattering experiment is designed to measure the scattering angle and the energy of alpha particles. The equipment consists of a Geiger counter, a source of alpha particles, and a detector.
• The Geiger counter is used to measure the scattering angle. The source of alpha particles is a radioactive element, such as polonium-210. The detector is a metal plate with a small hole in the center.
• When an alpha particle scatters off a metal atom, it loses energy. The amount of energy lost depends on the scattering angle. The detector measures the energy loss of the alpha particle.

Alpha Scattering Experiment

• The Alpha Scattering Experiment is a physics experiment used to measure the size of atomic nuclei.
• The experiment is performed by bombarding a sample of material with alpha particles and then measuring the angle and energy of the scattered particles.
• This data is used to calculate the size of the atomic nucleus.