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Questions and Answers
Who is credited with proposing the atomic theory?
Who is credited with proposing the atomic theory?
What does the Law of Conservation of Mass state?
What does the Law of Conservation of Mass state?
What is the fixed percentage by mass of hydrogen in water according to the Law of Constant Composition?
What is the fixed percentage by mass of hydrogen in water according to the Law of Constant Composition?
What is the correct formula to calculate the mass of Br reacted from the grams of SnBr4 formed and grams of Sn reacted?
What is the correct formula to calculate the mass of Br reacted from the grams of SnBr4 formed and grams of Sn reacted?
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What conclusion about the mass of unreacted KClO3 was reached in the example provided?
What conclusion about the mass of unreacted KClO3 was reached in the example provided?
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What is the mass of Br reacted when 3.0125 grams of Sn is reacted and 11.1086 grams of SnBr4 are formed?
What is the mass of Br reacted when 3.0125 grams of Sn is reacted and 11.1086 grams of SnBr4 are formed?
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In the experiment with tin and bromine forming tin tetrabromide, what principle does this scenario illustrate?
In the experiment with tin and bromine forming tin tetrabromide, what principle does this scenario illustrate?
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What key concept did Dalton use as a basis for his atomic theory?
What key concept did Dalton use as a basis for his atomic theory?
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Which scientist proposed the plum pudding model of the atom?
Which scientist proposed the plum pudding model of the atom?
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What significant discovery did Rutherford make through his gold foil experiment?
What significant discovery did Rutherford make through his gold foil experiment?
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What was a major scientific advancement in the mid 1980s relevant to atomic theory?
What was a major scientific advancement in the mid 1980s relevant to atomic theory?
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In Dalton's atomic theory, which concept was NOT included?
In Dalton's atomic theory, which concept was NOT included?
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What does the term 'Atomos' refer to in atomic theory?
What does the term 'Atomos' refer to in atomic theory?
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How did Thomson's cathode ray experiment contribute to atomic theory?
How did Thomson's cathode ray experiment contribute to atomic theory?
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What effect did Rutherford's findings about atomic structure have on previous theories?
What effect did Rutherford's findings about atomic structure have on previous theories?
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What was the primary conclusion of Rutherford's experiment with alpha particles and gold foil?
What was the primary conclusion of Rutherford's experiment with alpha particles and gold foil?
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What do the letters K, L, M, and N represent in the Bohr model of atomic structure?
What do the letters K, L, M, and N represent in the Bohr model of atomic structure?
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Which statement about electrons in an atom is correct?
Which statement about electrons in an atom is correct?
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What is the mass number of an atom?
What is the mass number of an atom?
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How are isotopes defined?
How are isotopes defined?
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What is the atomic number of an element?
What is the atomic number of an element?
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What does atomic weight represent?
What does atomic weight represent?
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Why are electrons considered to have 'basically no mass'?
Why are electrons considered to have 'basically no mass'?
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In a neutral atom, how do the number of protons compare to the number of electrons?
In a neutral atom, how do the number of protons compare to the number of electrons?
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Study Notes
Atomic Theory and Structure
- Democritus, a Greek philosopher, proposed the existence of the smallest indivisible particle, "atomos."
- Experimental evidence for the existence of atoms emerged in the 18th century.
- Mid-1980s saw the development of tools capable of directly observing individual atoms and molecules.
Dalton's Atomic Theory
- John Dalton proposed an atomic theory.
- This provided explanatory frameworks for important observations about matter.
Laws of Conservation of Mass
- Lavoisier, the "Father of Modern Chemistry," formulated the law of conservation of mass.
- This law asserts that the total mass of reactants equals the total mass of products in a chemical reaction.
Law of Constant Composition
- Also known as the law of definite proportions.
- This law posits that a compound always contains the same elements in the same proportion by mass.
- Water, for instance, always includes 11.1% mass of hydrogen and 88.9% mass of oxygen.
Dalton's Atomic Theory: Key Aspects
- Elements are composed of extremely small particles called atoms.
- All atoms of a given element are identical, but atoms of different elements differ.
- Atoms are neither created nor destroyed during chemical reactions; atoms of different elements rearrange.
- Compounds are formed when atoms of different elements combine in specific whole-number ratios.
Discovery of the Electron: J.J. Thomson's Model
- Thomson's cathode ray tube experiments led to the detection of negatively charged particles (electrons).
- He proposed the plum pudding model of the atom, where negatively charged electrons are embedded in a positively charged sphere.
Rutherford's Nuclear Model
- Rutherford's gold foil experiment demonstrated the presence of a dense, positively charged nucleus at the atom's center.
- Most alpha particles passed through the foil, but some were deflected.
- This suggested a small, massive, positively charged nucleus within the atom.
Bohr Model of Atomic Structure
- Bohr proposed a model where electrons orbit the nucleus in specific energy levels.
- Electrons can transition between levels by absorbing or emitting energy.
Modern Atomic Theory
- Electrons are not precise orbits but exist in electron clouds.
- It's impossible to pinpoint the exact location of electrons within an atom at any instant.
Atomic Structure: Subatomic Particles
- Atoms are composed of three fundamental particles:
- Protons: Positively charged, located in the nucleus, with a mass of approximately 1.
- Neutrons: Neutral, located in the nucleus, with a mass of approximately 1.
- Electrons: Negatively charged, orbiting the nucleus with a significantly smaller mass.
- A neutral atom has an equal number of protons and electrons.
Atomic Number and Mass Number
- Atomic number: The number of protons in an atom.
- Mass number: The sum of protons and neutrons in an atom.
Isotopes
- Atoms of the same element can have different numbers of neutrons but the same number of protons.
- Variations in neutron numbers result in different mass numbers without altering the chemical properties.
Atomic Weight
- Calculated as the average atomic mass of all naturally occurring isotopes of an element.
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Description
Explore the foundational concepts of atomic theory, including Democritus's early ideas, Dalton's atomic theory, and key laws governing mass and composition. This quiz will test your understanding of the important milestones and contributions in the development of atomic science.
