Podcast
Questions and Answers
Democritus theorized that matter could be divided until it reaches a point where it:
Democritus theorized that matter could be divided until it reaches a point where it:
- Turns into energy.
- Could still be visible to the naked eye.
- Becomes a liquid.
- Cannot be further divided. (correct)
The 'Four Elements Theory,' which included earth, wind, fire and water, was popularized by:
The 'Four Elements Theory,' which included earth, wind, fire and water, was popularized by:
- John Dalton.
- Democritus.
- Aristotle. (correct)
- Ernest Rutherford.
Which scientist is credited with proposing that the atom is an indivisible unit of an element?
Which scientist is credited with proposing that the atom is an indivisible unit of an element?
- Ernest Rutherford.
- J.J. Thomson.
- John Dalton. (correct)
- Niels Bohr.
Dalton's atomic model primarily suggested that all atoms of an element have the same:
Dalton's atomic model primarily suggested that all atoms of an element have the same:
J.J. Thomson's experiments led to the discovery of which subatomic particle?
J.J. Thomson's experiments led to the discovery of which subatomic particle?
Thomson's plum pudding model of the atom suggested that electrons are:
Thomson's plum pudding model of the atom suggested that electrons are:
Ernest Rutherford's gold foil experiment demonstrated that:
Ernest Rutherford's gold foil experiment demonstrated that:
In Rutherford's model, most of an atom's mass is concentrated in the:
In Rutherford's model, most of an atom's mass is concentrated in the:
Niels Bohr modified Rutherford's model by proposing that electrons:
Niels Bohr modified Rutherford's model by proposing that electrons:
According to Bohr's model, when do electrons jump to another shell?
According to Bohr's model, when do electrons jump to another shell?
In the Bohr atomic model, the first electron shell can hold a maximum of:
In the Bohr atomic model, the first electron shell can hold a maximum of:
According to Bohr's model, what is the maximum number of electrons the second and third shells can hold, respectively?
According to Bohr's model, what is the maximum number of electrons the second and third shells can hold, respectively?
What is the maximum number of electrons the first 20 elements can specifically hold per shell?
What is the maximum number of electrons the first 20 elements can specifically hold per shell?
The quantum mechanical model differs from the Bohr model by describing electrons as existing:
The quantum mechanical model differs from the Bohr model by describing electrons as existing:
Which atomic model is currently considered the most accurate and advanced?
Which atomic model is currently considered the most accurate and advanced?
Democritus named 'atom' from the Greek word 'atomos', which means:
Democritus named 'atom' from the Greek word 'atomos', which means:
In Rutherford's gold foil experiment, what observation led him to conclude that the atom consists mostly of empty space?
In Rutherford's gold foil experiment, what observation led him to conclude that the atom consists mostly of empty space?
Which of the following statements accurately describes the evolution of atomic models?
Which of the following statements accurately describes the evolution of atomic models?
How did Thomson know that atoms also contain positive charges?
How did Thomson know that atoms also contain positive charges?
What conclusion did Rutherford make about the existence of a positively charged nucleus that contains nearly all the mass of an atom?
What conclusion did Rutherford make about the existence of a positively charged nucleus that contains nearly all the mass of an atom?
Which of the following statements best describes the limitation of Dalton's atomic model?
Which of the following statements best describes the limitation of Dalton's atomic model?
Why is Quantum Mechanical Model more accurate than the Bohr Model?
Why is Quantum Mechanical Model more accurate than the Bohr Model?
What did people believe for 2000 years?
What did people believe for 2000 years?
What did Dalton suggest about masses of elements?
What did Dalton suggest about masses of elements?
What did Rutherford calculate about the size of the nucleus to the rest of the atom?
What did Rutherford calculate about the size of the nucleus to the rest of the atom?
Flashcards
Democritus's Theory
Democritus's Theory
Matter can be cut into tiny pieces until it reaches a point where it cannot be cut.
Four Elements Theory
Four Elements Theory
An earlier theory holds that all matter is made up of earth, wind, fire and water.
Dalton's Atomic Theory
Dalton's Atomic Theory
The indivisible unit of an element.
Dalton's Model of the Atom
Dalton's Model of the Atom
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Thomson's Discovery
Thomson's Discovery
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Positive Charges in Atoms
Positive Charges in Atoms
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Rutherford's Discovery
Rutherford's Discovery
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Atomic Nucleus
Atomic Nucleus
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Bohr's Model
Bohr's Model
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Electron Energy Levels
Electron Energy Levels
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Electron Shells
Electron Shells
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First Electron Shell
First Electron Shell
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Second and Third Electron Shells
Second and Third Electron Shells
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Quantum Mechanical Model
Quantum Mechanical Model
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Study Notes
Atomic Theory and the Structure of the Atom
Agenda
- Consists of a Ted Talk, notes and practice questions.
Discussion
- Exploring the history of scientific theories offers insight into how knowledge evolves and changes over time.
A Brief Atomic History
Democritus
- A greek philosopher who theorized that matter can be divided into smaller pieces until it reaches a point where it cannot be further divided
- He named this point the "atom", derived from the Greek word "atomos", meaning indivisible.
The Four Elements Theory
- Aristotle believed an existing theory claiming that all matter was comprised of four elements.
- Earth
- Wind
- Fire
- Water
- This was believed for 2000 years.
Western Understanding of the Atom Has Evolved
- 1803: Dalton proposed that the atom is the indivisible unit of an element
- 1904: Thomson discovered electrons
- Believed electrons resided within a sphere of uniform positive charge (the plum pudding model)
- 1911: Rutherford proved the existence of a positively charged nucleus
- The nucleus contains nearly all the mass of an atom
- 1913: Bohr proposed fixed circular orbits around the nucleus for electrons
- 1926: electrons occupy regions of space (orbitals) around the nucleus dependent on their energies.
John Dalton
- Modern atomic theory started gaining traction in the early 1800s
- John Dalton (1766-1844) considered the idea that each different kind of element is a unique kind of atom.
The Dalton Model
- He proposed that all atoms are small spheres that can vary in size, mass, or colour.
- Different atoms have different properties.
- All atoms within an element have identical properties like size and mass.
Thompson Model
- J.J. Thomson (1856-1940) researched the idea that atoms might be made from a combination of particles.
- He conducted an experiment that proved that atoms had negatively charged parts called electrons.
- Also states since atoms have no overall charge, atoms must contain positive charges.
The Gold Foil Experiment
- Ernest Rutherford (1871-1937) conducted an experiment where he shot positively charged particles at a very thin sheet of gold foil.
- Almost all the positive particles went right through the foil: however, about 1 in 10,000 positive particles bounced back
- These particles were deflected by something positively charged.
- Rutherford concluded by this that an atom has a nucleus in the centre
The Rutherford Model
- States the nucleus is a tiny positively charged part of the atom containing most of the atom's mass.
- Rutherford calculated that the size of the nucleus compared to the rest of the atom was like a single green pea compared to an entire area of a football field
The Bohr Model
- Niels Bohr (1885-1962) transformed the model of the atom into the modern understanding of today.
- His model demonstrated how electrons are arranged in different elements.
- Bohr suggested that electrons surround the nucleus in specific energy levels known as "shells."
- Electrons jump between these shells by gaining or losing energy.
- Each shell can contain a specific number of electrons.
- The first shell contains a maximum of 2 electrons.
- The second and third shells can contain up to 18 electrons each.
- The first 20 elements can only hold 8 electrons max per shell.
Quantum Mechanical Model
- The most advanced and accurate model of the atom, used today by chemists and physicists.
- Electrons do not exist as tiny points inside the atom, instead, they surround the nucleus in a form resembling a cloud.
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