Atomic Theory Timeline Flashcards
(9 cards)
Aristotle’s Four Element Theory
Belief: Matter is made of four elements—Earth, Water, Air, and Fire. He rejected atomic theory.
Model lacks Atomic Structure.
⚠️ Limitation: Lacked experimental proof and was later disproven by atomic discoveries.
Democritus’ Atomic Theory
💡 Belief: Matter is composed of tiny, indivisible particles called “atomos.”
Atoms are tiny, indivisible particles that make up all matter, like solid spheres.
⚠️ Limitation: No scientific evidence; overshadowed by Aristotle’s ideas.
John Dalton’s Atomic Theory
💡 Belief: Atoms are indivisible, combine in fixed ratios, and form compounds.
⚠️ Limitation: Did not account for subatomic particles like electrons.
J.J. Thomson’s Plum Pudding Model
💡 Belief: Atoms contain electrons embedded in a positive matrix. ⚠️
Model: Atoms are positively charged spheres with embedded electrons, like raisins in pudding.
Limitation: Did not explain the existence of the nucleus.
Ernest Rutherford’s Nuclear Model
💡 Belief: Discovered the nucleus—a dense, positively charged center.
Atoms have a dense, positively charged nucleus with electrons orbiting around it
⚠️ Limitation: Did not explain electron behavior or energy levels.
Niels Bohr’s Planetary Model
💡 Belief: Electrons orbit the nucleus in fixed energy levels.
Model: Electrons orbit the nucleus in fixed energy levels, like planets around the Sun.
⚠️ Limitation: Worked well for hydrogen but failed for larger atoms.
Erwin Schrödinger’s Quantum Model
💡 Belief: Electrons exist in probability clouds (orbitals), not fixed paths.
⚠️ Limitation: Hard to visualize; relies on mathematical probability.
James Chadwick’s Discovery of Neutrons
💡 Belief: Discovered neutrons, explaining atomic mass differences.
Atoms contain neutrons in the nucleus, explaining atomic mass differences.
⚠️ Limitation: Did not address electron behavior in quantum mechanics.
Modern Quantum Theory
💡 Belief: Atoms have a nucleus with protons and neutrons, surrounded by electrons in probability clouds. ⚠️ Limitation: Cannot predict exact electron locations, only probabilities.
