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What did Democritus name the smallest particles of matter?
Atoms
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What are the four elements that Aristotle included in his model of matter?
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How did John Dalton gather evidence for the existance of atoms?
He measured the masses of elements that reacted to form compounds.
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What theory did John Dalton propose to explain why the elements in a compound always join in the same way?
Dalton's Atomic Theory said that the elements were a fixed composition.
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What are the two main points of Dalton's Atomic Theory?
1. All elements are composed of atoms.
2. In a particular compound, atoms of different elements always combine in the same way.
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In Thompson's Theory of the Atom, what do objects with like electric charges do?
Repel each other (get away from me!)
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In Thompson's Theory of the Atom, what do objects with opposite electric charges do?
attract each other. (Ooo, I so luv you!)
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What happened to the beam when Thomson place a pair of charged metal plates on either side of the glass tube?
It bent.
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What did Thomson conclude when a pair of charged metal plates on either side of the glass tube bent the beam?
Thomson concluded that the particles in the glowing beam had a negative charge becaues they were attracted to a positive plate.
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Did Thomson's experiments provide the first evidence for the existence of subatomic particles?
Yep! Sure Did! Absolutley!
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Give a description of Thompson's model
It's like plum pudding scattered electrons in positive charge
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What is an alpha particle?
Rutherford's Atomic theory says that an alpha particle is a fast moving particle with a positive charge.
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What did Rutherford hypothesize would happen to the paths of alpha particles as they passed through a thin sheet of gold? (Two answers)
1. Most particles would travel straight from their source to a screen that lit up when struck.
2. Particles that did not pass straight through would be deflected.
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Name two things that happened when Marsden directed a beam of particles at a piece of gold foil?
1. More alpha particles were deflected than expected.
2. Some alpha particles bounced back toward the source.
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What did Rutherford conclude from the gold foil experiment?
An atom's positive charge is concentrated in its nucleus.
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Name three subatomic particles
- 1. proton
- 2. neutron
- 3. electron
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Which subatomic particle has a positive charge?
proton
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Why did Chadwick conclude that the particles produced by his experiment were neutral in charge?
He conculded that the particles produced were neutral in charge because charged objects didn't affect the path.
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Name three properties that vary among the subatomic particles.
- 1. mass
- 2. charge
- 3. location in the atom
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What is the expression that compares the masses of neutrons and protons?
mass of 1 neutron = mass of 1 proton
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Can two atoms of the same element have different numbers of protons?
No. Non. No way, Hosay. Not in this lifetime. No can do. Not gonna happen.
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What is an atomic number?
The atomic number equals the protons in an atom.
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The number of __________ and _____________ are always equal to an element's atomic number.
protons and electrons
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Can two different elements have the same atomic number?
Noooooooooooo!
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What is the mass number of an atom?
The mass number of an atom is the sum of the protons and the netrons.
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What is the equation for the number of neutrons?
Mass # - Atomic #
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Every Atom of a given element has the same number of what?
protons and electrons
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Every atom of a given element does not have the same number of what?
neutrons
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What are isotopes?
Isotopes are elements with extra or less neutrons.
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All oxygen atoms have 8 protons. How many neutrons in an atom of oxygen -18?
10
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Do isotopes of oxygen have different chemical properties?
Oui. Si. Ya.
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What is water that contains hydrogen -2 atoms instead of hydrogen-1 atoms called?
Heavy Water (I know this from watching Hogan's Heroes... an excellent WWII comedy show no child should miss!)
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How did Bohr's model of the atom differ from Rutherford's model?
Bohr's model focused on the electrons.
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In Bohr's model of the atom, do electrons have a constant speed and move in fixed orbits around the nucleus?
No sir! They are just all over the place zooming in and out around that nucleus randomly, fast and slow.
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When the atom gains or loses energy, what can happen to the electrons?
Electrons can move energy levels.
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What evidence do scientists have that electrons can move form one energy level to another?
The scientists measure the energy gained and lost.
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When electrons release energy, some of that energy may be released as what?
Visible light. (yes, really! It's true!)
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Was Bohr's model correct in assigning energy levels to electrons?
Yes. Bohr was DEAD-ON. (Now he's just DEAD.)
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What do scientists have to work with when trying to predict the locations and motions of electrons in atoms?
Probability (as in.... you will probably get this one right!)
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What is an electron cloud?
An electron cloud is a visual model of likely positions of an electron.
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Can scientists use the electron cloud model to describe the exact locations around the nucleus?
Nah. They can only guess... estimate... visualize where those electrons might be hanging out.
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What is an orbital?
An orbital is a region of space around the nucleus wher an electron is likely to be found.
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What is an electron model good for?
An electron model is a good approximation of the behaviour of electrons.
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Do higher energy levels have more or less orbitals than lower energy levels do?
MORE
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What is the relationship between the number of orbitals and the maximum number of electrons in an energy level?
The energy levels are squared and the orbits are doubled.
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What is an electron configuration?
An electron configuration is the arrngement of electrons in orbits.
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How many energy levels are needed for a lithium atom's three elements when the atom is in its gorund state?
Two
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Is it true that an excited state is less stable than a ground state?
Of course. (Beau is way less stable when he's excited!)
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When all of the electrons in an atom are in orbitals with the lowest possible energies, what do you know?
We know that the electrons are in the most stable configuration and that the atom is in its ground state.
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