Chapter 4
Pg. 100-118
Ancient Greek Models of Atoms
• __________– thought that all substances were built up from only ____
elements: earth, air, fire, and water
– matter could be divided an unlimited number of times
• __________– believed that all matter consisted of
extremely _____ particles that could
not be divided
– called particles atoms from the Greek
word ________, which means “uncut” or
“indivisible”
Dalton’s Atomic Theory
• ____________- born in England in 1766
– Teacher
– Interest in predicting the _______, led to his study
of the behavior of gases in air
-- Correctly concluded that a
gas consists of _________
_________
Dalton’s Atomic Theory
• Evidence for Atoms
– Measured the ______ of elements that combine
when compounds form.
– Noticed that no matter how _______ or _____the
sample, the ratio of the masses of the elements in
the compound is always the same (aka fixed
composition)
Dalton’s Atomic Theory
• ________ Theory- Dalton proposed the
theory that all matter is made up of individual
particles called ______, which cannot be
divided.
• Main Points of Theory
1. All elements are composed of ______.
2. All atoms of the same element have the same
mass, and atoms of ________ elements have
different masses.
Dalton’s Atomic Theory
• Main Points of Theory continued…
3. __________ contain atoms of more than one
element.
4. In a particular compound, atoms of different
elements always combine in the _____ _____
• Not all of Dalton’s ideas about atoms were
completely ______, but scientists did not
discard his theory, they revised it to take into
account new discoveries
Dalton’s Atomic Theory
Thomson’s Model of the Atom
• When rubbed, some materials gain the ability
to ______ or _____other
materials.
• Based on their ________, they
are said to have either
positive or negative electric
charges.
• Objects with ___ charges repel
or push apart.
Thomson’s Model of the Atom
• Objects with ________ charges attract, or pull
together.
• Some charged particles can flow from one
location to another. A flow of charged
particles is called an ________ _______
Thomson’s Model of the Atom
• J.J Thomson used _______ current to learn
more about atoms
Thomson’s Model of the Atom
• Thomson’s Experiment (pg. 102)
– __________ that the beam was a stream of
charged particles that interacted with the air in
the tube and cause the air to glow.
– Placed charged _____ plates at either end->
caused beam to deflect or bend
– Observed beam: ________ by negatively charged
plate and attracted by positively charged plate
Thomson’s Model of the Atom
• Evidence for Subatomic Particles
– Concluded that the particles in the beam had a
_________ charge because they were attracted to
the positive plate.
– Thomson’s experiments provided the _____
evidence that atoms are made of even ______
particles.
– Revised Dalton’s model to account for the
________ particles
Thomson’s Model of the Atom
• Thomson’s Model
– Atom is ______: meaning it has neither a negative
nor a positive charge
– Negative charges were evenly ________
throughout an atom filled with a positively
charged mass of matter
– “______ _______” model (may want to think of
chocolate chip ice cream)
Thomson’s Plum Pudding Model
Rutherford’s Atomic Theory
• _____, Rutherford
discovered that
uranium emits fastmoving particles
that have a positive
charge called _____
________
Rutherford’s Atomic Theory
• Hypothesis: (asked student- _______, to find
out what happens to alpha particles when
they pass through a thin sheet of gold)
Predicted that most particles would travel in a
_______ path from their source to a screen
that lit up when struck.
Rutherford’s Atomic Theory
• The _______ ______ Experiment
– Aimed narrow beam of alpha particles at gold, the
material around the ______ produced a flash of
light when struck by fast-moving alpha particles
– Could figure out ____ of alpha particles by
observing the flash after they had passed through
the gold
– Did _____ support Rutherford’s prediction
Rutherford’s Atomic Theory
• Gold Foil Experiment continued…
– More particles were deflected than he expected
– About 1 out of every ______ was deflected by
more than 90 degrees
– Some alpha particles behaved as though they had
struck an object and bounced _______ back
Gold Foil Experiment
Rutherford’s Atomic Theory
• Discovery of the Nucleus
– Alpha particles whose paths were ________ must
have come close to another charged object
– The closer they came, the greater the deflection
– _________: the positive charge of an atom is not
evenly spread throughout the atom, it is
concentrated in a very small central area- ______
– Nucleus: a dense, positively charged mass located
in the center of the atom
Rutherford’s Atomic Theory
• According to Rutherford’s model, all of an
atom’s _______ charge is concentrated in its
nucleus
Chapter 4 Section 2
Pg. 108-112
Properties of Subatomic Particles
• Protons, electrons, and neutrons are
_________ particles
• Protons:
– A __________charged subatomic particle that is
found in the nucleus of an atom
– Positive charge (amount varies among elements),
each proton is _____
– Each _________ must contain at least one particle
with a positive charge
Properties of Subatomic Particles
• Electrons
– Comes from Greek word meaning “______”
– A _________ charged subatomic particle that is
found in the space outside the nucleus
– Each electron has a charge ____
Properties of Subatomic Particles
• Neutrons
– 1932, English physicist J. _________ designed an
experiment to show that neutrons exist;
concluded particles were ________ because a
charged object did not deflect their path
– A neutral subatomic particle that is found in the
nucleus of an atom
– ______ is almost exactly equal to that of a proton
Comparing Subatomic Particles
• Protons, electrons, and neutrons can be
distinguished by _____, charge, and location
in an atom.
• Protons and neutrons have almost the _____
mass
• It would take about 2,000 electrons to equal
the mass of one proton
• Protons and neutrons are _______ nucleus,
electrons are in outside space
Atomic Number and Mass Number
• ______ predicted that the atoms of any
element are different from the atoms of all
other elements
• Atomic Number
– atoms of any given element always have the same
number of protons
– Atomic number of an _______ equals the number
of protons in an atom of that element
– _______ of different elements have different
numbers of protons
Atomic Number and Mass Number
• Mass Number
– the mass number of an atom is the ____ of the
protons and neutrons in the nucleus of that atom.
– Ex: an atom of Al with 13 protons and 14 neutrons
has a mass number of 27
Atomic mass is the same
as mass number
Isotopes
• Every atom of a given element _____
_____have the same number of neutrons.
• Isotopes are atoms of the same element that
have different numbers of neutrons and
different mass numbers
• Isotopes of an element have the ____ atomic
number but different mass numbers because
they have different number of neutrons
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Chapter 4 Section 3
Pg. 113-118
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Bohr’s Model of the Atom
• Bohr was a ______ physicist who worked with
Rutherford
• Bohr _______ with Rutherford’s model, but
Bohr’s model focused on the electrons
• Energy Levels
– In Bohr’s model, _________ move with constant
speed in fixed orbits around the nucleus (like
planets around a sun)
Bohr’s Model of the Atom
• Energy Levels
– Each ________ in an atom has a specific amount
of energy
– If an atom _____ or ______energy, the energy of
an electron can change
– The possible energies that electrons in an atom
can have are called ______ _______
– An electron cannot exist between energy levels
Bohr’s Model of the Atom
• Energy Levels
– An electron in an atom can _____ from one
energy level to another when the atom gains or
loses energy
– The _____ of the jump between energy levels
determines the amount of energy gained or lost
• Evidence for Energy Levels
– Scientists can measure the energy _______ or
released when an electron absorbs or releases
energy and moves to higher or lower energy levels
Bohr’s Model of the Atom
Electron Cloud Model
• An electron cloud is a ______ model of the
most likely locations for electrons in an atom
• The cloud is _______ at those locations where
the probability of finding an electron is high
• Scientists use the electron
cloud model to describe the
possible _______ of electrons
around the nucleus
Atomic Orbitals
• The ______ _____ represents all the orbitals
in an atom
• An orbital is a region of space around the
nucleus where an ______ is likely to be found
• An electron cloud is a good approximation of
how electrons behave in their orbitals
Atomic Orbitals
• Level which an electron has the ____ energy–
the lowest energy level– has only one orbital
• Higher energy levels have _____ than one
orbital
• Each orbital can contain _____ electrons at
most
Electron Configurations
• An electron configuration is the __________
of electrons in the orbitals of an atom
• The most ______ electron configuration is
the one in which the electrons are in orbitals
with the _______ possible energies
• When all the electrons in an atom have the
_______ possible energies, the atom is said to
be in its ground state
Electron Configurations
• If a lithium atom ______ enough energy, one
of its electrons can move to an orbital with a
higher energy, this ____________ is referred
to as an excited state
• An excited state is _____ stable than the
ground state
• Eventually the electron _____ _______and
the atom returns to the ground state
Electron Configuration
• Helium, neon, argon, krypton, and xenon
atoms _________ from excited states to the
______ state emit the light you see in “neon”
lights