Atomic Theory and Models Quiz

Basic Postulates:
1. All matter is composed of indivisible particles called atoms.
2. Atoms of a given element are identical in mass and properties.
3. Atoms cannot be created or destroyed in chemical reactions.
4. Compounds are formed by the combination of atoms in fixed ratios.
Significance:
- Laid the groundwork for modern chemistry.
- Introduced the concept of the atom as the smallest unit of matter.

Key Features:
- Proposed by J.J. Thomson in 1897 after discovering the electron.
- Atoms consist of a positively charged 'soup' (the pudding) with negatively charged electrons (the plums) embedded within it.
Limitations:
- Failed to explain the structure of the atom and the existence of the nucleus.

Experiment Overview:
- Conducted by Ernest Rutherford in 1909.
- Directed alpha particles at a thin gold foil.
Observations:
- Most alpha particles passed through the foil, some were deflected at large angles, and a few bounced back.
Conclusions:
- Atoms are mostly empty space.
- A dense, positively charged nucleus exists at the center of the atom.

Key Concepts:
- Introduced by Niels Bohr in 1913.
- Electrons orbit the nucleus in defined paths or energy levels (orbits).
Postulates:
1. Electrons travel in fixed orbits around the nucleus without radiating energy.
2. Energy is absorbed or emitted when an electron jumps from one orbit to another.
Limitations:
- Only accurately described hydrogen and failed for more complex atoms.

Fundamental Principles:
- Developed in the 1920s from the work of scientists like Schrödinger and Heisenberg.
- Electrons exist in probability clouds or orbitals rather than fixed paths.
Key Features:
- Uses wave functions to describe the behavior and location of electrons.
- Incorporates principles of quantum mechanics, including uncertainty principle.
Implications:
- Provides a more accurate depiction of atomic structure and electron behavior.
- Recognizes the dual nature of electrons (wave-particle duality).

All matter consists of indivisible particles known as atoms.
Atoms of an element are identical in mass and properties, distinguishing them from others.
Atoms cannot be created or destroyed; they remain unchanged during chemical reactions.
Compounds form from the combination of atoms in specific ratios.
Established foundational concepts for modern chemistry and defined the atom as the smallest unit of matter.

J.J. Thomson proposed this model in 1897 upon discovering the electron.
The model describes atoms as a positively charged 'soup' with negatively charged electrons (the 'plums') mixed throughout.
It does not account for atomic structure or the presence of a nucleus.

Conducted by Ernest Rutherford in 1909, involving the bombardment of thin gold foil with alpha particles.
Observations revealed that most alpha particles passed through, some were deflected, and a few bounced back.
Concluded that atoms are primarily empty space and contain a dense, positively charged nucleus at their center.

Introduced by Niels Bohr in 1913, proposing that electrons orbit the nucleus in defined energy levels or shells.
Key postulates state that electrons travel in fixed orbits without radiating energy and can absorb or emit energy when transitioning between orbits.
However, the model accurately describes only hydrogen atoms, failing to account for more complex atomic structures.

Developed in the 1920s by prominent scientists such as Schrödinger and Heisenberg.
This model suggests that electrons exist in probability clouds or orbitals rather than fixed paths, emphasizing the uncertainty in their location.
Utilizes wave functions to portray electron behavior, incorporating quantum mechanics principles and the wave-particle duality of electrons.
Represents a more reliable depiction of atomic structure and the behavior of electrons.