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theory

1. THEORY

2. Solid Sphere Atoms are dense and solid, with no internal structure or subatomic particles considered. Plum Pudding Atoms are described as uniform, positively charged spheres with electrons embedded within them, similar to raisins in a pudding. Nuclear Atom consists of a small, dense, positively charged nucleus at the center, with electrons orbiting around it, similar to planets orbiting around the sun. Planetary Electrons move in quantized, discrete energy levels around the nucleus and emit or absorb energy when transitioning between levels. Quantum Electrons do not have definite orbits, but are described by wave functions that represent probability distributions of their locations. ATOMIC THEORY TIMELINE John Dalton J.J. Thomson Ernest Rutherford Niels Bohr Erwin Schrödinger 1803 1897 1911 1913 1920s

3. British chemist and physicist Proposed the Solid Sphere Model in the early 19th century JOHN DALTON 1766 - 1844 Shifted from philosophical ideas to scientific theory First atomic model based on experimental evidence and quantitative observations Paved the way for the development of modern atomic theories

4. According to this theory, atoms are tiny balls that can't be broken and are all made of the same material. This theory helped explain how different chemicals mix together and what makes them different. ATOMIC THEORY 1803 Couldn’t explain differences in atomic mass within an element (isotopes) Didn’t account for the presence of subatomic particles like protons, neutrons, and electrons Couldn’t explain the behavior of atoms in chemical reactions LIMITATIONS SOLID SPHERE MODEL

5. English physicist known for his work on the nature of electrons Proposed the Plum Pudding Model in the late 19th century Discovered electrons as distinct particles Shifted understanding from indivisible atom to subatomic particles Paved the way for further exploration of atomic structure J.J. THOMSON 1856 - 1940

6. According to this theory, atoms are like plum pudding, with tiny positive charges scattered throughout a cloud of negative electrons. This theory helped explain why atoms have a neutral charge overall and why they emit light when they collide with each other. ATOMIC THEORY 1897 Couldn’t explain why electrons didn’t collapse into the positive sphere Failed to predict the distribution and arrangement of electrons Lacked explanation for the nucleus and its positive charge LIMITATIONS PLUM PUDDING MODEL

7. New Zealand-born physicist known for his contributions to nuclear physics Introduced the Nuclear Model in the early 20th century ERNEST RUTHERFORD 1871 - 1937 First model to propose a central, massive nucleus Explained the behavior of positively charged alpha particles in the gold foil experiment Laid the groundwork for understanding atomic structure and radioactivity

8. According to this theory, atoms have a nucleus with a positive charge and most of the mass, surrounded by electrons that orbit like planets. It explains why particles can pass through or bounce off atoms, and is the basis of our current understanding of atomic structure. ATOMIC THEORY Didn't explain the stability of the nucleus against electrostatic repulsion Lacked details about electron orbits and energy levels Didn't incorporate the principles of quantum mechanics LIMITATIONS 1911 NUCLEAR MODEL

9. Danish physicist known for his pioneering work in atomic structure Proposed the Planetary Model in the early 20th century Explained atomic spectra with precision Introduced the concept of quantized energy levels Bridged classical physics with emerging quantum mechanics NIELS BOHR 1885 - 1962

10. According to this theory, electrons orbit the nucleus of an atom in specific energy levels or shells. This theory helped explain why atoms emit light and why they absorb certain colors of light. It also helped explain the stability of atoms and why they don't fall apart. ATOMIC THEORY 1913 Limited to explaining the hydrogen atom Couldn't account for the behavior of multi-electron atoms Didn't incorporate the wave-like nature of electrons LIMITATIONS PLANETARY MODEL

11. Austrian physicist renowned for his contributions to quantum mechanics Proposed the Quantum Model in the 1920s ERWIN SCHRÖDINGER 1887 - 1961 Quantum mechanics provides a comprehensive understanding of electron behavior Schrödinger's model successfully explains multi-electron atoms Quantum mechanics is the foundation of modern atomic theory

12. According to this theory, electrons exist as a probable wave-like pattern around the nucleus, not in a specific orbit. It explains why electrons act like particles and waves, and is the foundation of our understanding of atomic structure and widely used in modern physics. ATOMIC THEORY 1920s Mathematical complexity of the model Requires advanced mathematics to calculate electron probabilities Doesn't provide a simple visual representation of atomic structure LIMITATIONS QUANTUM MODEL

13. Time to test your knowledge of the THEORY

14. IF ATOMS ARE SOLID SPHERES, WHAT WOULD HAPPEN IF YOU TRIED TO CUT ONE IN HALF? Type your response here. ANSWER QUESTION

15. IF ATOMS ARE SOLID SPHERES, WHAT WOULD HAPPEN IF YOU TRIED TO CUT ONE IN HALF? In the Solid Sphere Model, atoms were believed to be indivisible, so you couldn't actually cut one in half. It was thought that atoms were the smallest, fundamental building blocks of matter. ANSWER QUESTION

16. HOW WOULD YOU DESCRIBE THE DISTRIBUTION OF "RAISINS" (ELECTRONS) IN THIS ATOMIC PUDDING? Type your response here. ANSWER QUESTION

17. HOW WOULD YOU DESCRIBE THE DISTRIBUTION OF "RAISINS" (ELECTRONS) IN THIS ATOMIC PUDDING? In the Plum Pudding Model, the "raisins" (electrons) were thought to be scattered throughout the positive "pudding" (atom). So, the distribution of electrons was assumed to be relatively uniform within the atom. ANSWER QUESTION

18. WHAT DID RUTHERFORD'S GOLD FOIL EXPERIMENT REVEAL ABOUT THE ATOMIC NUCLEUS? Type your response here. ANSWER QUESTION

19. WHAT DID RUTHERFORD'S GOLD FOIL EXPERIMENT REVEAL ABOUT THE ATOMIC NUCLEUS? Rutherford's gold foil experiment revealed that most of the atom's mass is concentrated in a small, positively charged nucleus at the center. This discovery overturned the idea of a uniformly distributed positive charge. ANSWER QUESTION

20. WHY MIGHT ELECTRONS BE COMPARED TO PLANETS IN A SOLAR SYSTEM WITHIN BOHR'S MODEL? Type your response here. ANSWER QUESTION

21. WHY MIGHT ELECTRONS BE COMPARED TO PLANETS IN A SOLAR SYSTEM WITHIN BOHR'S MODEL? Bohr's Planetary Model drew an analogy between electrons orbiting the nucleus and planets orbiting the sun. It simplified the complex behavior of electrons, suggesting they had quantized energy levels like planets have orbits. ANSWER QUESTION

22. WHY MIGHT ELECTRONS BE COMPARED TO PLANETS IN A SOLAR SYSTEM WITHIN BOHR'S MODEL? How does Schrödinger's cat relate to the concept of electron probability clouds in the Quantum Model? ANSWER QUESTION

23. WHY MIGHT ELECTRONS BE COMPARED TO PLANETS IN A SOLAR SYSTEM WITHIN BOHR'S MODEL? Schrödinger's cat is a thought experiment in quantum mechanics, not directly related to electrons. However, it illustrates the probabilistic nature of quantum systems, similar to how electrons are described by probability clouds in the Quantum Model. The cat is in a superposition of states (both alive and dead) until observed, much like electrons can exist in multiple states until measured. ANSWER QUESTION

24. THE DEVELOPMENT OF ATOMIC THEORY Atoms were first conceptualized by the early Greeks 1 Plum Pudding Model 2 Planetary Model 4 Nuclear Model 3 Quantum Model 5