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Theories on Atomic Structure - Coggle Diagram
Theories on Atomic Structure
Dalton's Atomic
theory
Dalton's atomic theory, proposed by John Dalton in the early 19th century, is a foundational concept in chemistry. It states that all matter is composed of atoms, which are indivisible and indestructible. Atoms of a given element are identical in mass and properties, while atoms of different elements differ in mass and properties. Compounds are formed when atoms of different elements combine in simple whole number ratios. Chemical reactions involve the rearrangement of atoms, but the atoms themselves are not changed
*Strengths:
Dalton's theory successfully explained the law of conservation of mass (matter cannot be created or destroyed) and the law of definite proportions (a chemical compound always contains the same elements in the same proportion by mass).
Introduced the concept of atomic weights:
Dalton's theory provided a framework for understanding the relative weights of different elements.
Distinguished between elements and compounds:
Dalton's theory differentiated between elements, composed of identical atoms, and compounds, formed by combinations of different atoms.
Weaknesses:
Indivisible atoms:
Identical atoms of an element:
Dalton assumed that all atoms of a given element are identical, but this is not true due to the existence of isotopes (atoms of the same element with different masses).
No internal structure:
Dalton's theory didn't explain the internal structure of atoms, including the arrangement of electrons, protons, and neutrons.
No explanation for chemical bonding:
The theory didn't explain how atoms combine to form molecules or the forces that hold them together.
Cannot explain allotropes:
Dalton's theory couldn't explain allotropes, different forms of the same element with different properties (e.g., diamond and graphite).
Ernest Rutherford
Theory
Ernest Rutherford was a New Zealand-born British physicist who made groundbreaking contributions to the understanding of atomic structure and radioactivity. He is best known for his gold foil experiment, which led to the discovery of the nucleus and the realization that atoms are mostly empty space. He also discovered alpha and beta radiation and proposed the theory of radioactive decay.
Strengths
:
Discovered the nucleus.
Explained scattering of alpha particles.
Weaknesses:
Electrons should lose energy and spiral into the nucleus (unstable).
Couldn’t explain atomic spectra.
Niels Bohr
Theory
Niels Bohr, a Danish physicist, proposed a model of the atom to explain how electrons behave around the nucleus. He combined classical and early quantum ideas to improve on Rutherford’s atomic model.
Strengths:
Explained stability of atom.
Matched hydrogen spectrum well.
Weaknesses
:
Failed for multi-electron atoms.
Still considered electrons as particles in fixed paths (not accurate).
Erwin Schrödinger
theory
Erwin Schrödinger's atomic model, also known as the quantum mechanical model, treats electrons as waves and introduces the concept of electron orbitals as regions of probability rather than fixed paths. This model, developed in 1926, built upon previous atomic models and incorporated the wave-particle duality of electrons.
Strengths
Accurate for all atoms, including multi-electron systems (unlike Bohr's model).
Explains the structure of the periodic table and chemical bonding.
Introduces probability-based orbitals, aligning with experimental results.
Forms the foundation of modern quantum chemistry.
Helps explain atomic spectra, molecular shapes, and reactivity.
Weaknesses
Very complex mathematically—requires advanced knowledge to understand or solve the equations.
Does not provide a simple visual model of the atom, making it harder for beginners to grasp.
Only gives probabilities of where an electron might be, not exact positions or paths.
James Chadwick
Theory
James Chadwick's atomic model, proposed after his 1932 discovery of the neutron, included a nucleus composed of protons and neutrons, with electrons orbiting around it. This model built upon previous atomic models by adding the neutron, a neutral particle, to the nucleus alongside the positively charged protons.
Strengths
Completed the atomic model by identifying the third major subatomic particle.
Helped explain isotopes—atoms with the same number of protons but different masses due to differing neutrons.
Laid the foundation for nuclear physics and nuclear reactions (e.g., nuclear fission).
Essential for the development of atomic bombs and nuclear energy.
Weaknesses
Did not propose a new atomic model, just added to the existing one (like Rutherford-Bohr’s).
His discovery didn’t explain electron behavior or energy levels.
Though crucial, the neutron's role in chemical behavior is minimal, since chemical reactions mainly involve electrons.
