Download Chapter 3 Atoms: The Building Blocks of Matter

Date __________________
Chapter 3 Atoms: The Building Blocks of Matter
The Structure of the Atom
 An ______ is the __________ particle of an element that retains the __________
__________ of that element.
 All atoms consist of _____ regions:
1) ________- a very small region located near the ______ of an atom. Every
nucleus contains at least one _________ _________ _________
called a ________ and usually one or more __________
___________called _________.
2) Surrounding the nucleus is a region occupied by _________ _________
_________ called _________.
 Protons, neutrons, and electrons are often referred to as ________ ________.
 A proton has a positive charge _______ ___ ___________ to the negative charge
of an electron.
 Atoms are electrically neutral because they _________ ________ __________ of
protons and electrons.
 A neutron is electrically neutral.
 A proton has a mass ______ ______ ________ than the mass of an electron.
 All atoms besides the __________ _________ ______ also contain neutrons.
 The nuclei of atoms of different elements ______ in the number of protons they
contain and therefore in the ________ ___ ________ _______ they possess.
 The ________ ___ ________ in an atom's nucleus determines that ______
_________.
 There are short-range proton-neutron, proton-proton, and neutron-neutron forces
that hold the nuclear particles together called ________ ________.
 The radius of an atom is the distance from the center of the nucleus to the outer
portion of the electron cloud.
 Atomic radii are so small they are expressed in picometers. There are 10
picometer in 1 meter.
Atomic Number
 The________ _________ of an element is
the number of _______ in the nucleus of
each atom of that element.
Date ___________________
 Look at the periodic table, elements are placed in order of ___________ atomic
number. The atomic number identifies an element. Because atoms are neutral,
the atomic number also tells you how many __________ that atom contains.
Isotopes
 The simplest atoms are those of hydrogen. All hydrogen atoms contain only one
proton. However, hydrogen atoms can contain __________ _________ ___
_________.
 Protium, deuterium, and tritium are isotopes of hydrogen. Isotopes are atoms of
the same _________ that have different _________.
Mass Number
 The isotopes of a particular element all have the __________________________
________________________________.
 The ______ _________ is the _________________________ in the nucleus of an
isotope.
Designating Isotopes
 Isotopes usually do not have distinct names like hydrogen's isotopes. Instead
isotopes are usually specified by their ______ _________.
 Two methods for specifying isotopes:
1) ________ __________ - the mass number is written with a hyphen after the
name of the element. Example: uranium-235
2) ________ __________ - the mass number is written as the superscript and the
subscript is the atomic number.
mass number - atomic number = number of neutrons
235 (protons + neutrons) - 92 protons = 143 neutrons
 _________ is a general term for any isotope of any element.
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Date ___________________
Relative Atomic Masses
Because the masses of atoms expressed in grams are very small, it is more convenient to
use __________ _________ _______.
The standard used by scientist for units of atomic mass is the ___________ ________. It
has been assigned a mass of exactly 12 _________ ______ ______ or 12 ____.
One_________ ______ ______, or 1 amu, is exactly 1/12 the mass of a carbon-12 atom.
Average Atomic Masses of Elements
Most elements occur naturally as __________ of _________.
Calculating weighted averages:
Suppose you have a box containing two sizes of marbles. If 25% of the marbles
have masses of 2.00 g each and 75% have masses of 3.00 g each, what is the weighted
average calculated?
________ ________ ______ is the weighted average of the atomic masses of the
_________ _________ isotopes of an element.
Multiply the mass of each marble by the decimal fraction representing its percentage in
the mixture. Then add the products.
(2.00 g x 0.25) + (3.00 g x 0.75) = 2.75 g
Calculating Average Atomic Mass
The average atomic mass of an element depends on both the _____ and the _________
___________ of each of the element's isotopes.
Naturally occurring copper consists of 69.17 % copper-63, which has an atomic mass of
62.929 598 amu, and 30.38% copper-65 which has an atomic mass of 64.927 793 amu.
(0.6917 x 62.929 598 amu) + (0.3038 x 64.927 793 amu) = 63.55 amu
An element's atomic mass is usually round to _____ ________ _______ before it is used
in a calculation.
Relating Mass to Numbers of Atoms
A _____ (mol) is the amount of a substance that contains as many particles as there are
atoms in exactly 12 g of carbon-12.
The mole is a __________ _____ like a dozen is.
___________ ________ is 6.022 x 1023. That's the number of particles in exactly one
mole of a pure substance.
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Date ___________________
The mass of one mole of a pure substance is called the _______ ______ of that
substance. Its units are ______. The molar mass is numerically equal to the ________
______ of the element in atomic mass units (which is found on the periodic table).
Gram/Mole Conversions
What is the mass in grams of 3.50 mol of the element copper, Cu?
What is the mass in grams of 2.25 mol of the element iron, Fe?
What is the mass in grams of 0.375 mol of the element potassium, K?
What is the mass in grams of 0.0135 mol of the element sodium, Na?
What is the mass in grams of 16.3 mol of the element nickel, Ni?
A chemist produced 11.9 g of aluminum, Al. How many moles of aluminum were
produced?
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Date ___________________
How many moles of calcium, Ca, are in 5.00 g of calcium?
How many moles of gold, Au, are in 3.60 x 10-10 g of gold?
Avogadro's Number Conversions
How many moles of silver, Ag, are in 3.01 x 1023 atoms of silver?
How many moles of lead, Pb, are in 1.50 x 1012 atoms of lead?
How many moles of tin, Sn, are in 2500 atoms of tin?
How many atoms of aluminum, Al, are in 2.75 mol of aluminum?
What is the mass in grams of 1.20 x 108 atoms of copper, Cu?
What is the mass in grams of 7.5 x 1015 atoms of nickel, Ni?
What mass of gold, Au, contains the same number of atoms as 9.0 g of aluminum, Al?
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Date ___________________
Chapter 3 Scientists that contributed to Atomic Theory
The Philosophical Idea of the Atom
 The ____________ ____________ of ____________ was supported as early as 400
B.C. by certain Greek thinkers, such as _____________. He called nature’s basic
particle an _________, based on the Greek word meaning “indivisible”.
 _____________ on the other hand, did not believe in ________. He thought that all
matter was continuous, and his opinion was accepted for nearly 2000 years.
 Neither view was supported by experimental evidence, so each remained speculation
until the eighteenth century. Then scientists began to gather evidence favoring the
______________________________________.
Foundations of Atomic Theory
 The transformation of a substance or substances into one or more new substances is
known as a ____________ ____________.
 In the 1790s, the study of matter was revolutionized by a new emphasis on the
________________ analysis of chemical reactions. Aided by improved
_____________, investigators began to accurately measure the _________ of the
elements and compounds they were studying. This lead to the discovery of several
basic laws:
 The _______ ____ ____________________ ____ ________ states that mass is
neither destroyed nor created during ordinary chemical reactions or physical
changes.
 The _______ ____ ________________ ________________
o Example from previous test:
 The _______ ____ ________________ ________________
o Example from previous test:
Dalton’s Atomic Theory
 In 1808, an English schoolteacher named _______ __________ proposed an
explanation for these three laws. He reasoned that elements were composed of
atoms and that only __________ _____________ of atoms can combine to form
compounds. His theory can be summed up by the following statements.
1. _______________________________________________________________
_________________________________________________________________
_________________________________________________________________
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Date ___________________
2. _______________________________________________________________
_________________________________________________________________
_________________________________________________________________
3. _______________________________________________________________
_________________________________________________________________
_________________________________________________________________
4. _______________________________________________________________
_________________________________________________________________
_________________________________________________________________
5. _______________________________________________________________
_________________________________________________________________
_________________________________________________________________
Modern Atomic Theory
 By relating atoms to the measurable property of mass, Dalton turned Democritus’s
idea into a ______________ ____________ that could be tested by experiment. But
not all aspects of Dalton’s atomic theory have proven to be correct.
 For example, today we know that atoms are ___________ into even smaller
particles (although the law of conservation of mass still holds true for chemical
reaction). Also a given element can have atoms with different ________, called
____________.
 Not all of the atomic theory has been discarded. Instead it has been modified to
explain the new observations. The important concepts that (1) all matter is
composed of atoms and that (2) atoms of any one element differ in properties from
atoms of another element, remain unchanged.
Discovering the Structure of the Atom
The Electron
 Discovered during investigations into the relationship between ___________ and
matter.
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Date ___________________
 Current was passed through a _______________ and scientist noticed that the
tube glowed. The glow was a stream of particles that they called a
_____________. The ray flowed from the _________ (negative terminal) to the
_________ (positive terminal). Observation from these experiments:
 The cathode rays were deflected by a magnetic field that was negatively
charged. (That must mean the cathode ray was made of ___________
_________ __________ because they were deflected or repelled by the
negative magnetic field.)
 __________________________ conducted more experiments with cathode
rays. He was able to measure the ___________________ of an electron. It
was always the same no matter what _______ or ______ was used. So all
cathode rays were composed of identical negatively charged particles which
were named _________. Since it didn’t matter what gas or metal was used it
was concluded that electrons were present in
____________________________________.
 YIKES! That means the atom is divisible!
 __________________________ performed the ______________________
which was able to measure the _______ ________ of an electron. Using
Thomson’s charge-to-mass ratio he was able to determine the _______ of the
electron.
 It was extremely small. _________ the mass of the simplest atom,
hydrogen.
 Two inferences were made once the electron was discovered:
 The atom must also contain ___________ charged particles since atoms are
electrically _________.
 Since electrons are so extremely small, the other particles that make up an atom
must account for most of their _______.
 Thomson proposed the _______________________. He said the negative
electrons were spread evenly throughout the positive charge of the rest of the
atom. Think of a watermelon: the seeds are the electrons; the fruit is the positive
charge. The seeds do not contribute much to the overall mass of the watermelon.
This model was ___________ with further experimentation.
The Nucleus
 _____________________ and associates performed the
_________________________ .
 Shot a thin piece of _____ _____with fast moving ______ particles (_________
________) If the charge and mass were uniform throughout the atom the alpha
particles should pass straight through.
 1 in 8000 alpha particles _______________ to the source! What did this mean???
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Date ___________________
 The alpha particles must have hit some powerful force and since it only
happened 1 in 8000 times the force had to take up a very small _________
___ ________. Since the alpha particles are positive they must have been
__________ by positive charge.
 Rutherford called this small, dense bundle of positive charge the _________.
 Now we know where the positive charge is located…where are the electrons
located?
In 1913, Danish physicist _________ _________ proposed a model of the
_____________ ________. According to the model, the electron can circle the nucleus
only in __________ ________, or ___________.
The electron is in its ____________ ____________ ____________ when it is in the
___________ ___________ to the ___________.
The __________ is separated from the nucleus by a large empty space where the
___________ cannot exist.
The __________ of the ___________ is higher when it is in __________ that are
successively farther from the nucleus.
The ____________ ____________ ____________ of an atom is its ____________
__________.
A state in which an atom has a _________ ______________ __________ than it has in
its ground state is an ____________ __________.
While in orbit, the electron can neither ________ nor ________ energy. It can,
however, move to a __________ ___________ __________.
Visible light is a kind of _____________ ___________,
which is a form of energy that exhibits wavelike behavior
as it travels through space.
A ________ is a particle of electromagnetic radiation
having zero mass and carrying a quantum of energy.
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Date ___________________
The success of _______ ________ of the hydrogen atom led many scientists to conclude
that a similar model could be applied to all atoms. However, Bohr’s approach _____
_____ _________ the spectra of atoms with _______ _______ _____ __________. Nor
did Bohr’s theory explain the ___________ ___________ ___ _______.
The Quantum Model of the Atom
In 1924, the French scientist Louis de Broglie hypothesized that electrons had a dualnature. Electrons have the behavior of both particles and waves. This was confirmed
with diffraction experiments that showed electrons bend, or diffract just like waves. De
Broglie suggested that electrons be considered waves confined to the space around an
atomic nucleus.
If electrons are both waves and particles, where are they in the atom???
In 1927, the German physicist _________ ______________ proposed that there is
always an _____________ in trying to locate an electron because of the way they are
detected.
ANALOGY: Think of a mouse running through a dark house. If you hear the mouse and point a
flashlight at it, the mouse will turn and run in a different direction than it would have gone without the
light.
The ________________ ________________ ________________ states that it is impossible to
determine simultaneously both the position and velocity of an electron or any other particle.
In 1926, the Austrian physicist _________ _______________ developed an equation that treated
electrons in atoms as waves using the hypothesis that electrons have a dual-nature.
From these two ideas, we realized that electrons do not travel around the nucleus in neat orbits, as Bohr had
postulated. Instead, they exist in certain regions called ___________. An ___________ is a three-dimensional
region around the nucleus that indicates the probable location of an electron.
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