Development of Atomic Model Flashcards
(15 cards)
What was the earliest concept of the atom, and who proposed it?
The earliest concept of the atom is attributed to Democritus, who proposed atomic theory, the idea that all matter is made up of tiny, indivisible particles called atoms, separated by empty space.
Democritus lived around 500 BC.
How did John Dalton build upon Democritus’s ideas?
John Dalton revived and expanded upon atomic theory in the early 1800s, describing atoms as solid, indivisible spheres and suggesting that different elements were made up of different types of these spherical atoms.
This laid the groundwork for understanding chemical elements and their combinations.
What was J.J. Thomson’s contribution to the model of the atom?
J.J. Thomson discovered negatively charged particles, known as electrons, through his experiments with cathode rays in 1897, proposing the ‘plum pudding’ model, where the atom was envisioned as a ball of positive charge with electrons embedded within it.
This model challenged the idea of solid atoms.
What experiment did Ernest Rutherford conduct and what did it reveal?
Ernest Rutherford conducted the gold foil experiment in 1909, firing positively charged alpha particles at gold foil, which revealed that some particles were deflected at large angles, indicating a concentrated positive charge in a small nucleus.
This led to the proposal of the nuclear model of the atom.
What was the major flaw in Rutherford’s nuclear model of the atom?
A significant problem with Rutherford’s model was that it couldn’t explain why atoms didn’t collapse, as classical physics suggested that orbiting electrons should lose energy and spiral into the nucleus.
This indicated instability in the atomic structure.
How did Niels Bohr’s model improve upon Rutherford’s?
Niels Bohr proposed that electrons orbit the nucleus in specific, fixed energy levels or shells, addressing instability by preventing electrons from spiraling into the nucleus.
This concept of quantized electron energy levels was a crucial advancement.
What further discoveries refined the model of the atom after Bohr’s work?
Further discoveries included the identification of protons as discrete particles in the nucleus by Rutherford and the discovery of neutrons by James Chadwick.
This refined the understanding of nuclear structure.
How does the modern understanding of the atom compare to Bohr’s model?
The modern understanding incorporates quantum mechanics, describing electron behavior in terms of probability distributions or orbitals, while maintaining the structure of a nucleus with protons and neutrons surrounded by electrons in energy levels.
This builds upon Bohr’s foundational contributions.
Fill in the blank: The earliest concept of the atom is attributed to _______.
Democritus
True or False: John Dalton described atoms as indivisible spheres.
True
Fill in the blank: The ‘plum pudding’ model was proposed by _______.
J.J. Thomson
Fill in the blank: The concentrated positive charge in the nucleus was identified by _______ through the gold foil experiment.
Ernest Rutherford
True or False: Electrons in Bohr’s model could exist in any energy level.
False
Fill in the blank: The particles discovered by James Chadwick in the nucleus are called _______.
neutrons
What did quantum mechanics contribute to the modern understanding of the atom?
Quantum mechanics describes electron behavior in terms of probability distributions or orbitals rather than fixed orbits.
This represents a significant shift from classical models.
