Chapter 3 Atoms: The Building Blocks of Matter

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Chapter 3 Atoms The Building Blocks of Matter

• Section 3-1 The Atom From Philosophical Idea
  to Scientific Theory

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The first people to think about particle theory
were the _____________ around ___________.

• Greeks
• 400 BC

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One in particular was __________. The word atom
in Greek means _______.

• Democritus
• indivisible

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Following Democritus was _________. He didnt
believe in atoms. He thought matter was
___________.

• Aristotle
• continuous

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This idea succeeded for about _______years.
Neither view was supported by __________
_________ until ________.

• 2000
• experimental evidence
• The 18th century

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By the late ________, most people thought of an
_______ as something that could not be broken
down and that could _________ with other elements
to form __________.

• 1800s Atom
• combine compounds

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Scientists still werent sure, however if they
always combined in the same ________.

• proportions

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In the late 1790s scientists had better
_________ which allowed them to study chemical
reactions ___________.

• balances
• quantitatively

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This led to the law of _______________________.
It essentially says that as long as nothing
enters or leaves a chemical reaction, _______
remains constant.

• conservation of mass
• mass

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Antoine-Laurent de Lavoisier

• He was obsessed with measuring mass during
  chemical reactions.
• He observed that when chemical reactions are
  carried out in a closed system, the mass of the
  system is not changed.

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• He was obsessed with the latest equipment for
  measuring mass.
• He spent a great deal of the French taxpayers
  money on this equipment.
• He died in the French Revolution.

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It also lead to the law of __________________
which essentially says that regardless of the
_________ or _________ of the sample, the
elements that make it up are always there in the
same ____________.

• definite composition
• size or source
• proportions

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Law of Definite Proportions
Joseph Louis Proust (1754-1826)
Joseph Louis Proust observed that Copper
carbonate (CuCO3) occurs in nature as the mineral
malachite (a), it forms as a patina on copper
roofs (b) and bronze statues, and can also be
synthesized in the laboratory (c). Regardless of
its source, basic copper carbonate has the same
composition.
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Since the composition of copper carbonate is the
identical regardless of the source, Proust called
this generalization as the law of definite
proportions.
Swedish chemist Berzelius heated certain amount
of lead with various amount of sulfur. He found
that when he used 1.55 g of sulfur (yellow) and
10.0 g of lead (gray) he got 11.55 of lead
sulfide (black).
Jons Jacob von Berzelius 1779-1848
If sulfur were taken in excess of 1.55g,
Berzelius found that the excess amount of sulfur
did not react. Similarly if had 1.55 g of sulfur
and added lead in excess of 10.0 g, he found that
the excess lead did not react
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The law of definite proportions Berzelius View
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Definite proportions A Closer Look
The law of definite proportions. Berzelius'
experiment with lead and sulfur are interpreted
in terms of Dalton's atomic theory.
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The electrolysis of water
Henry Cavendish (1731 - 1810) further illustrated
the law of definite proportion by electrolyzing
water.
Electrolysis of water. During electrolysis, water
decomposes to give hydrogen gas and oxygen gas
always in a 2-to-1 volume ratio when energy is
supplied by a battery or other source of direct
current (dc).
http//wps.prenhall.com/wps/media/objects/439/4499
69/Media_Portfolio/Chapter_04/Electrolysis_of_Wate
r.MOV
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More complicated is the law of ______________.
It says that if ______ or more different _______
are made of the same 2 elements, the ratio of the
________ element combined with a fixed mass of
the 1st element is always a ________ of small
___________ numbers

• multiple proportions two
• 2nd ratio
• whole

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An example of this would be the compounds of
___________ and ___________.

• carbon dioxide
• carbon monoxide

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John Daltons Atomic Theory of Multiple
Proportions
Dalton theory multiple proportions Elements can
combine with each other in more than one set of
proportions.
For example, hydrogen and oxygen combine with
each other in two different proportions and form
two entirely different compounds.
John Dalton (1766-1848)
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Although these two molecules contain only
hydrogen and oxygen, they are not the same
compound.
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These three laws prompted John Dalton to propose
his atomic theory. It basically says
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1. All matter is made of ______________
______________ called ____________

• indivisible
• indestructible
• atoms

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2. Atoms of the same ___________ are chemically
and physically the ________.

• element
• same

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3. Atoms of ___________ elements are chemically
and physically the ________.

• different
• different

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4. When atoms _______ in a chemical reaction,
they do so in ___________, ____________ number
ratios.

• combine
• small
• whole

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In a chemical reaction, atoms arent ____________
or ____________, they are simply _____________.

• created
• destroyed
• rearranged

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Section 3-2 The Structure of the Atom
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Atoms consist of ___________________ regions.
One of them contains the ___________________ and
___________________. It is called the
___________________.

• 2
• protons neutrons
• nucleus

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The other area surrounds the nucleus. It
contains ___________________ particles called
___________________.

• negatively charged
• electrons

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Actually ___________________, ___________________,
and ___________________ are all
___________________.

• protons neutrons
• electrons subatomic particles

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The electron was discovered by working with a
tube that contained a ___________________ at very
low pressure.

• gas

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When ___________________ passed through it, it
would light up. It is called a
_____________________________________.

• an electrical current
• cathode ray tube

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The fact that the ray was deflected by a negative
charged showed that the ray had a
___________________ charge.

• negative

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The fact that the ray could move a paddle wheel
demonstrated the ___________________ nature of
the ray.

• particle

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The ray was actually made of ___________________.

• electrons

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The scientist credited with naming the
___________________ was ___________________.

• electron
• JJ Thomson

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It stands to reason that where there is a
negative charge, there must be a
___________________ charge to balance it.

• positive

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_________________________ and associates tried to
bombard ___________________ with
___________________.

• Ernest Rutherford
• gold
• alpha particles

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They expected that most of the a particles would
________________________.

• go straight thru (92)

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For the most part, this was true, but some were
___________________ and a very small percentage
were actually _____________________.

• deflected (6)
• shot straight back (2)

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It took 2 years, but Rutherford developed a 2
part explanation. It was

• Atoms are mostly empty space
• Atoms must have a densely packed positively
  charged nucleus.

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To summarize the ___________________,
___________________ are the lightest and can be
found ______________________. They have a
________________ charge.

• subatomic particles electrons
• orbiting the nucleus
• negative

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___________________ and ___________________ are
the heaviest and are found in the
___________________.

• Protons
• neutrons
• nucleus

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___________________ have a positive charge and
___________________ have ___________________
charge.

• Protons
• neutrons
• no

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Section 3-3 Counting Atoms
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neutral, atomic number, chlorine, proton, 17,
electron

• A neutral atom of chlorine would have 17 protons
  and 17 electrons if it is neutral.
• Because chlorine has an atomic number of 17, it
  would have 17 protons and assuming it is neutral,
  it would have 17 electrons.

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isotope, tritium, deuterium, protium, atomic
mass, 1, 2, 3, hydrogen

• The three isotopes of hydrogen are protium with
  an atomic mass of 1, deuterium with an atomic
  mass of 2, and tritium with an atomic mass of 3.
• Hydrogen has 3 different isotopes. They are
  protium, deuterium, and tritium with atomic
  masses of 1, 2, and 3 respectively.

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nuclide, superscript, subscript, hyphen notation,
uranium, nuclear symbol

• You can indicate nuclides 2 different ways
  Hyphen notation means you write the symbol with a
  dash and the atomic mass or you could use the
  nuclear symbol method where you write the symbol
  and put the atomic mass as a subscript to the
  upper left and the atomic number as a subscript
  to the lower left.

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Example

• U-238

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carbon-12, atomic mass unit

• An atomic mass unit is defined as one twelfth of
  a carbon-12 atom.

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average atomic mass, isotopes, percentage,
naturally occurring

• The average atomic mass of an element takes into
  account the percentages of the naturally
  occurring isotopes.
• Average atomic mass can be calculated by
  multiplying the atomic masses of the isotopes by
  their naturally occurring percentage in a mixture.

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mole, carbon-12, Avogadros number, molar mass

• A mole is defined as 12 g of the carbon-12
  isotope. It has Avogadros number of atoms. The
  molar mass of all other elements is compared to a
  mole of carbon-12.

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Subatomic Particles
The atoms of all elements consists of positively
charged protons, neutral neutrons and negatively
charged electrons. The protons and the neutrons
together are called as nucleons and they are
located at the nucleus of the atoms.
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The Atomic Number
The number of protons in the nucleus of an atom
determines the atomic number (Z) and indicates
the element's identity. For a neutral atom, the
atomic number also describes the number of
electrons around the nucleus.
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Atomic Mass and Atomic Number
Mass number A (sum of protons and neutrons)
? Atomic number Z (number of protons)
number of neutrons.
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Isotopes of hydrogen
While the number of protons in the nucleus
defines an element's identity, variations on the
number of neutrons in the nucleus give rise to
different isotopes of the same element.
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Mass Numbers and Atomic Numbers
The atomic number is equal to the number of
protons in an atom of that element. The mass
number is the sum of the number of protons and
neutrons.