Atomic Theory and Models Quiz

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Questions and Answers

Which scientist proposed that all matter is composed of extremely small particles called atoms?

J.J. Thompson

John Dalton (correct)

Ernst Rutherford

Democritus

What did J.J. Thompson discover about the structure of the atom?

Electrons are negatively charged particles. (correct)

Atoms consist only of neutrons.

Atoms are indivisible.

Atoms have a dense nucleus.

What does the Law of Definite Proportions state?

Compounds can vary in proportions.

All atoms of an element have different properties.

Elements can combine in fixed ratios. (correct)

Atoms cannot be subdivided.

What was Max Planck's contribution to atomic theory?

Energy is emitted in discrete quantities. (C) Signup and view all the answers

Which scientist is known for the Planetary Model of the atom?

Niels Bohr (D) Signup and view all the answers

What did Rutherford's Gold Foil Experiment demonstrate about the atom?

Atoms have a dense nucleus surrounded by electrons. (A) Signup and view all the answers

How did Albert Einstein explain the photoelectric effect?

Light is made up of particles called photons. (C) Signup and view all the answers

According to early atomic theory, what feature of atoms was emphasized by Dalton?

Atoms cannot be divided. (B) Signup and view all the answers

What significant conclusion did Rutherford reach from his experiments regarding atomic structure?

Atoms contain a dense nucleus surrounded by electrons. (C) Signup and view all the answers

How did Niels Bohr contribute to the understanding of electron behavior in atoms?

He stated that electrons can only exist in fixed orbits around the nucleus. (C) Signup and view all the answers

What theory did Max Planck introduce regarding energy emission and absorption?

Energy can be emitted only in specific, discrete quantities. (D) Signup and view all the answers

What is the implication of the Law of Definite Proportions in terms of atomic composition in compounds?

Compounds are always formed from elements in fixed ratios by mass. (B) Signup and view all the answers

Which model depicts the atom as having a positive mass with negatively charged electrons dispersed throughout it?

Plum-Pudding Model (A) Signup and view all the answers

What is the key idea of Dalton's atomic theory regarding elements?

Elements are composed of only one type of atom. (B) Signup and view all the answers

Which particle did Rutherford hypothesize must exist alongside protons in the atomic nucleus?

The neutron (D) Signup and view all the answers

What did Albert Einstein's explanation of the photoelectric effect reveal about light?

Light behaves both as a wave and as a stream of particles. (A) Signup and view all the answers

Study Notes

Atomic Theory

Democritus hypothesized that matter could be divided into smaller and smaller pieces until a point where it could no longer be divided. He called this indivisible piece an atom.
John Dalton proposed that all matter is composed of atoms.
Atoms of the same element are identical in size, mass, and chemical properties.
Atoms of different elements are different.
Atoms cannot be subdivided, created or destroyed.
Atoms combine in whole number ratios to form compounds.

J.J. Thomson

Discovered negatively charged particles (electrons)
Proposed the plum pudding model, describing atoms as a sphere of positive charge with negatively charged electrons embedded within it.

Ernest Rutherford

Conducted the gold foil experiment.
Discovered a dense, positively charged nucleus at the center of the atom.
Proposed the nuclear model of the atom, with electrons orbiting the nucleus.
Suggested the existence of the neutron, a neutral particle in the nucleus that contributes to the mass of the atom.

Rutherford's Experimental Design

Alpha particles (positively charged) are directed at a thin gold foil.
Most alpha particles passed straight through, suggesting that atoms are mostly empty space.
Some alpha particles were deflected, indicating a dense, positively charged nucleus. Alpha particles were deflected by a positive nucleus.

Max Planck

Observed that excited gases under low pressure emit light at specific wavelengths (line spectra), indicating that energy is emitted in discrete quantities.
Introduced the concept of quanta, the smallest packet of energy that can be absorbed or emitted.

Niels Bohr

Proposed the planetary model of the atom, with electrons orbiting the nucleus in specific, allowed energy levels.
Electrons can only exist in specific energy levels (quantized energy).

Albert Einstein

Explained the photoelectric effect, suggesting that light behaves as a stream of particles (photons).
Each photon has a specific energy, and if this energy is high enough, it can cause an electron to jump to a higher energy level.

Louis de Broglie

Proposed that electrons, like light, possess both wave-like and particle-like properties (wave-particle duality).

Erwin Schrödinger

Developed a model where electrons are described by probability distributions (orbitals) rather than precise paths.
Electrons are found in regions of space called orbitals, where the probability of finding them is highest.
The concept of precisely determining an electron's location and momentum is impossible (Uncertainty Principle). The position or momentum of an electron cannot be precisely determined simultaneously (Uncertainty Principle).

Homework Assignment

Read pages 143-146.
Answer questions 1-3, 10 on page 147.
Read pages 148-151.
Answer questions 1, 3 on page 152.

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Description

Test your knowledge on atomic theory, including the contributions of Democritus, John Dalton, J.J. Thomson, and Ernest Rutherford. This quiz covers fundamental concepts about atoms, their structure, and how they combine to form compounds.