Delta Sigma Theta Pop-up Shop Group

Public·140 members

May 26, 2023

Early History Of The Atom Homework Answers

If you are looking for early history of the atom homework answers, you have come to the right place. In this article, we will review some of the key concepts and experiments that shaped our understanding of the atomic structure. We will also provide some links to helpful resources where you can find more information and practice questions.

Early History Of The Atom Homework Answers

Download Zip

John Dalton and the Atomic Theory

One of the first scientists to propose a theory about atoms was John Dalton, an English chemist who lived in the late 18th and early 19th century. Dalton's atomic theory stated that:

All elements are composed of tiny indivisible particles called atoms.

All atoms of the same element are identical in mass and properties.

Atoms of different elements have different masses and properties.

Atoms combine in simple whole-number ratios to form compounds.

Atoms cannot be created or destroyed in chemical reactions.

Dalton's theory was based on his observations of chemical reactions and the law of conservation of mass. He also devised a system of symbols to represent different elements and compounds.

J.J. Thomson and the Electron

In the late 19th century, J.J. Thomson, an English physicist, discovered a new subatomic particle: the electron. He used a device called a cathode ray tube, which consisted of a glass tube with two metal electrodes connected to a high-voltage source. He observed that a beam of particles, called cathode rays, was emitted from the negative electrode (cathode) and traveled to the positive electrode (anode). He also found that the beam was deflected by electric and magnetic fields, indicating that it was composed of negatively charged particles.

Thomson's discovery proved that atoms were not indivisible, as Dalton had assumed, but had smaller components. He proposed a new model of the atom, called the plum pudding model, in which the atom was a sphere of positive charge with electrons embedded in it, like currants in a pudding.

Ernest Rutherford and the Nucleus

In 1909, Ernest Rutherford, a New Zealand-born physicist, conducted a famous experiment that challenged Thomson's plum pudding model. He used a thin sheet of gold foil and a source of alpha particles, which are positively charged particles emitted by radioactive elements. He directed a beam of alpha particles at the gold foil and detected them with a screen coated with zinc sulfide, which produced flashes of light when hit by alpha particles.

Rutherford expected that most alpha particles would pass through the foil with little or no deflection, as predicted by Thomson's model. However, he observed that while most alpha particles did go through the foil, some were deflected at large angles or even bounced back. This indicated that there was something very dense and positively charged in the center of the atom that repelled some alpha particles.

Rutherford proposed a new model of the atom, called the nuclear model, in which the atom had a small but massive nucleus that contained most of the positive charge and mass of the atom, surrounded by a cloud of electrons that occupied most of the volume but had little mass. He also calculated that the nucleus was about 10,000 times smaller than the atom.

Conclusion

The early history of the atom is full of discoveries and innovations that advanced our knowledge of matter and its structure. Dalton's atomic theory laid the foundation for modern chemistry, Thomson's discovery of the electron revealed a new level of complexity within atoms, and Rutherford's experiment showed that atoms had a nucleus that contained most of their mass and charge. These ideas were further refined and modified by later scientists, such as Niels Bohr, James Chadwick, and Erwin Schrödinger.

If you want to learn more about early history of the atom homework answers, you can check out these resources:

Early ideas about atoms - Atomic structure - AQA - GCSE Chemistry (Single Science) Revision - AQA - BBC Bitesize

History of the Atom Worksheet

Early History of the Atom Homework - Lesson Planet

Niels Bohr and the Bohr Model

In 1913, Niels Bohr, a Danish physicist who worked with Rutherford, improved the nuclear model by introducing the concept of quantum theory. He proposed that electrons can only occupy certain orbits around the nucleus, each with a fixed energy level. He also explained that electrons can jump from one orbit to another by absorbing or emitting a quantum of light, called a photon. The energy of the photon is equal to the difference between the energy levels of the orbits.

Bohr's model was able to explain the emission spectrum of hydrogen, which consists of discrete lines of different colors corresponding to different wavelengths of light. Each line represents a transition of an electron from a higher energy orbit to a lower energy orbit. For example, when an electron jumps from the second orbit (n=2) to the first orbit (n=1), it emits a photon of red light with a wavelength of 656 nanometers.

Bohr's model was also able to calculate the radius and energy of each orbit using some simple mathematical formulas. For example, the radius of the nth orbit is given by:

where n is the quantum number, h is Planck's constant, m is the mass of the electron, k is Coulomb's constant, and e is the charge of the electron.

Limitations of the Bohr Model

Although Bohr's model was very successful in explaining the hydrogen atom, it had some limitations and drawbacks. Some of them are:

It could not explain the spectra of atoms with more than one electron, such as helium and lithium.

It could not explain the fine structure and hyperfine structure of spectral lines, which are caused by small variations in energy levels due to relativistic effects and interactions between electrons and nucleus.

It could not explain the Zeeman effect and the Stark effect, which are changes in spectral lines due to external magnetic and electric fields.

It violated the Heisenberg uncertainty principle, which states that it is impossible to know both the position and momentum of an electron simultaneously with absolute precision.

It assumed that electrons move in circular orbits with constant speed, which contradicts the wave nature of electrons.

Therefore, Bohr's model was later replaced by more advanced models based on quantum mechanics, such as the Schrödinger model and the Pauli exclusion principle.

Conclusion

The early history of the atom homework answers can help you understand how scientists developed different models of atomic structure based on experimental evidence and theoretical concepts. Dalton's atomic theory introduced the idea of atoms as indivisible particles of matter. Thomson's discovery of electrons showed that atoms have subatomic components with negative charge. Rutherford's experiment revealed that atoms have a small but dense nucleus with positive charge. Bohr's model incorporated quantum theory and explained how electrons can emit or absorb light when they change orbits. However, Bohr's model also had some limitations and was superseded by more sophisticated models based on quantum mechanics.

If you want to learn more about early history of the atom homework answers, you can check out these resources: