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Questions and Answers
How did Thomson's experiments with cathode ray tubes contribute to the understanding of atomic structure?
How did Thomson's experiments with cathode ray tubes contribute to the understanding of atomic structure?
- They revealed the existence of electrons, negatively charged particles present in all atoms. (correct)
- They demonstrated that atoms are indivisible and the smallest unit of matter.
- They led to the discovery of the neutron and its role in atomic mass.
- They proved that atoms have a dense, positively charged nucleus.
How did Rutherford's gold foil experiment change the atomic model?
How did Rutherford's gold foil experiment change the atomic model?
- It demonstrated a small, dense, positively charged nucleus.
- Both B and C (correct)
- It revealed that atoms are mostly empty space.
- It confirmed the plum pudding model by showing electrons are evenly distributed.
Which statement accurately describes the behavior of atoms during chemical and nuclear reactions, according to modern atomic theory?
Which statement accurately describes the behavior of atoms during chemical and nuclear reactions, according to modern atomic theory?
- Atoms are always conserved; they can neither be subdivided nor destroyed in any reaction.
- Atoms cannot be subdivided in ordinary chemical reactions, but they can be changed in nuclear reactions. (correct)
- Atoms can be subdivided during ordinary chemical reactions, but are conserved in nuclear reactions.
- Atoms are only conserved in reactions involving radioactive isotopes.
How does the mass number of an atom relate to the number of protons and neutrons in its nucleus?
How does the mass number of an atom relate to the number of protons and neutrons in its nucleus?
What is the main difference between isotopes of the same element?
What is the main difference between isotopes of the same element?
How is the atomic mass of an element calculated considering the existence of isotopes?
How is the atomic mass of an element calculated considering the existence of isotopes?
Which of the following statements accurately describes a conclusion drawn from the study of electrons?
Which of the following statements accurately describes a conclusion drawn from the study of electrons?
If an atom has an atomic number of 20, what does this indicate?
If an atom has an atomic number of 20, what does this indicate?
How does the periodic table organize elements based on their atomic structure?
How does the periodic table organize elements based on their atomic structure?
Consider an isotope of oxygen with 8 protons and 10 neutrons. What is its mass number?
Consider an isotope of oxygen with 8 protons and 10 neutrons. What is its mass number?
Why is the nucleus considered to contain most of the mass of an atom?
Why is the nucleus considered to contain most of the mass of an atom?
How do the properties of atoms of one element compare to those of another element?
How do the properties of atoms of one element compare to those of another element?
What experimental evidence led Rutherford to conclude that the nucleus of an atom is positively charged?
What experimental evidence led Rutherford to conclude that the nucleus of an atom is positively charged?
Which of the following is a correct pairing of a subatomic particle with its corresponding charge?
Which of the following is a correct pairing of a subatomic particle with its corresponding charge?
Which property of cathode rays was observed to be consistent, regardless of the element used in the cathode ray tube?
Which property of cathode rays was observed to be consistent, regardless of the element used in the cathode ray tube?
Flashcards
Atomic Theory
Atomic Theory
Atoms cannot be subdivided, created, or destroyed in ordinary chemical reactions, but they can be in nuclear reactions.
Atomic mass uniqueness
Atomic mass uniqueness
Each element has a unique, characteristic average mass.
Isotopes
Isotopes
Atoms of the same element can differ in mass due to isotopes.
Electron properties
Electron properties
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Atomic neutrality
Atomic neutrality
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Massive atom components
Massive atom components
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Nucleus
Nucleus
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Rutherford's gold foil findings
Rutherford's gold foil findings
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Nucleus properties
Nucleus properties
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Electron
Electron
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Proton
Proton
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Neutron
Neutron
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Atomic number (Z)
Atomic number (Z)
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Mass number
Mass number
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Isotopes definition
Isotopes definition
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Study Notes
- Students must know how to relate an element's place on the periodic table to its atomic number and mass.
- It is crucial to know that an atom's nucleus is far smaller than the overall atom but comprises most of its mass.
Modern Atomic Theory
- In normal chemical reactions, atoms cannot be created, divided, or destroyed.
- Atoms can change in nuclear reactions.
- Each element has an average mass unique to it.
- Atoms of different elements differ in property.
Discovery of the Electron
- J.J. Thomson used a cathode ray tube in 1897 to identify negatively charged particles.
- Cathode ray tubes run electricity through a low-pressure gas.
Conclusions from Electron Study
- Cathode rays' properties are the same no matter the element used to create them.
- All elements have identically charged electrons.
- The presence of positive particles is vital to balance the negative charge of electrons since atoms are neutral.
- Atoms contain other particles that account for the bulk of the mass because electrons have minimal mass.
Thomson’s Atomic Model
- Electrons are like plums in a positively charged "pudding" - the "plum pudding" model.
Rutherford’s Gold Foil Experiment
- Rutherford's experiment utilized alpha particles, which are helium nuclei.
- Alpha particles were directed at a thin gold sheet.
- Particle strikes were noted on a screen
Rutherford’s Findings
- The majority of particles passed straight through the gold foil.
- Deflection occurred in a small number of particles.
- Only a few particles experienced considerable deflections.
- The nucleus is small, dense and positively charged.
Atomic Particles
| Particle | Charge | Mass # | Location |
|---|---|---|---|
| Electron | -1 | 0 | Electron cloud |
| Proton | +1 | 1 | Nucleus |
| Neutron | 0 | 1 | Nucleus |
Atomic Number
- The atomic number (Z) indicates the number of protons in an element's atom's nucleus and is unique for each element.
- Carbon has 6 protons and an atomic number of 6.
- Phosphorus has 15 protons and an atomic number of 15.
- Gold has 79 protons and an atomic number of 79.
Mass Number
- The mass number equals the number of protons plus neutrons in an isotope's nucleus.
- Oxygen-18 has 8 protons, 10 neutrons, and a mass number of 18.
- Arsenic-75 has 33 protons, 42 neutrons, and a mass number of 75.
- Phosphorus-31 has 15 protons, 16 neutrons, and a mass number of 31.
Isotopes
- Isotopes refer to atoms of the same element but with varying numbers of neutrons, resulting in different masses.
- Hydrogen-1 (protium) has 1 proton, 1 electron, and 0 neutrons.
- Hydrogen-2 (deuterium) has 1 proton, 1 electron, and 1 neutron.
- Hydrogen-3 (tritium) has 1 proton, 1 electron, and 2 neutrons.
Atomic Masses
- Atomic mass represents the average mass of an element's naturally occurring isotopes.
- Carbon-12 has 6 protons and 6 neutrons, comprising 98.89% of naturally occurring carbon.
- Carbon-13 has 6 protons and 7 neutrons, accounting for 1.11% of carbon found in nature.
- Carbon-14 consists of 6 protons and 8 neutrons, making up less than 0.01% of carbon in nature.
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