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Chapter 4 Study Guide
Section 1
 Vocabulary: nucleus
 What did Aristotle believe about matter?
o All matter came from 4 elements: air, water, fire, earth
o Matter could be divided an unlimited number of times
 What did Democritus believe about matter?
o Matter was made of tiny particles called atoms that could not be
divided.
 What was Dalton’s theory?
o All matter is made of atoms that cannot be divided
 What did Dalton’s model of the atom look like?
A solid sphere
 What type of evidence did Dalton gather for his atom?
He measured the masses of compounds and found the ratio of
elements in compounds to always be the same
 What was Thomson’s experiment?
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Cathode ray tube
 How did Thomson change Dalton’s model of the atom? What did Thomson’s
model look like?
It looked similar to a chocolate chip cookie. All of the atom was
positive with negative particles scattered throughout.
 What do we call Thomson’s model of the atom?
Plum pudding model
 What did Rutherford discover in addition to the alpha particles emitted by
uranium? The nucleus
 What was Rutherford’s experiment (include the name)?
The goldfoil experiment: alpha particles were shot at a piece of
goldfoil and when the surrounding material was hit by the particles it flashed
light.
 How did Rutherford change the model of the atom? What did his model look
like?
Rutherford said the positive charge was concentrated in the center of
the atom (the nucleus) with the electrons moving around the outside of the
nucleus.
Section 2
 Vocabulary: proton, electron, neutron, atomic number, mass number,
isotopes
 Protons:
o What charge does a proton have? positive
o Where is the proton located? nucleus
 Electrons:
o What charge does an electron have? negative
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o Where is the electron located? Space outside the nucleus
o Electron comes from a Greek word meaning what? amber
Neutron:
o What charge does a neutron have? neutral
o Where is the neutron located? nucleus
o Who discovered the neutron? Chadwick
How do the masses of protons, neutrons, and electrons compare?
o Protons and neutrons are close to the same mass. Electrons are much
smaller than protons and neutrons.
Know that atoms of different elements have different numbers of protons.
The atomic number tells you the number of what two subatomic particles?
o Protons and electrons
What is the mass number?
o Protons plus neutrons
How do you find the number of neutrons?
o Atomic mass minus atomic number
What are isotopes?
o Isotopes of the same element have the same number of protons and
electrons, but a different number of neutrons and atomic mass.
Compare and contrast hydrogen-1 and hydrogen-2.
o H-1: 1 proton, 0 neutrons, 1 electron, mass of 1
o H-2: 1 proton, 1 neutron, 1 electron, mass of 2
Section 3
 Vocabulary: energy levels, electron, cloud, orbital, electron configuration,
ground state
 What was Bohr’s focus?
o electrons
 What did his model of the atom look like?
o Nucleus in the center with “rings” of energy levels
 What do we know about energy levels?
o Electrons cannot exist between levels. Electrons can move to other
energy levels when energy is lost or gained.
 What happens when electrons gain or lose energy?
o They move to a different energy level
 What state is it when electrons absorb energy?
o Excited state
 What state is it when an electron loses energy?
o Ground state
 What is the most stable electron configuration?
o When all electrons are in the lowest possible energy levels (ground
state)
 What do scientists use the electron cloud model for?
o To describe the possible locations of electrons around the nucleus.
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When Neon atoms return from excited states to the ground state, what
happens? Energy is emitted in the form of light
*Make sure you can complete an example of Bohr’s model.
*Be able to label all of the parts of an atom.
* Be able to fill in a table of missing information on atomic number, atomic
mass, number of protons, neutrons, and electrons. (Like the homework sheet)