Download x 1011

2/3/2016
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Today

Reminders:
◦ What are atoms made of?
◦ Problem Set 1 DUE online
next Monday at 11 pm
 Protons
 Neutrons
 Electrons
 Sizes, Masses, Volumes
◦ Scientific Notation
 Using exponents to express
large and small numbers
 Converting between standard
notation & scientific notation
Orders of Magnitude:
Scientific Notation

A tool for expressing incredibly large or incredibly small
numbers WITHOUT using lots of zeros.
◦ Scientific notation is the combination of a
exponential of 10 (10x).
and an
Example:
There are approximately 400,000,000,000 stars in our galaxy.
x 1011
1011 = 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 =
100,000,000,000
In proper scientific notation: The decimal part of the
number is always expressed somewhere between 1 
n < 10.
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Scientific Notation

A positive exponent (n) means 1 multiplied by 10 n times.
104 = 10 ∙ 10 ∙ 10 ∙ 10 = 10,000

To change a number that is 10 or greater to scientific
notation: count how many times you must move the
decimal to the left to change the number to something
between 1 and less than 10.
◦ The number you counted is the number of factors of 10 you are
dividing out of the number and will be the exponent on the 10 in
scientific notation.
Scientific Notation

A negative exponent (-n) means 1 divided by 10 n times.
10−4 =

1
1
1
=
=
= 0.0001
104 10 ∙ 10 ∙ 10 ∙ 10 10,000
To change a number less than 1 to scientific notation:
count how many times you must move the decimal to the
RIGHT to change the number to something between 1 and
less than 10.
◦ That number is the number of factors of 10 you are multiplying
into the number and the negative of that number will be the
exponent on the 10 in scientific notation.
Scientific Notation
Expressing extremely small and extremely large numbers

◦

Atoms are very small.
For example, 18 mL (~ 4 teaspoons) of water contains
602,200,000,000,000,000,000,000 molecules of H2O.
A single water molecule has a mass of 2.99 x 10-26
grams.
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Theories of Matter Composition
Democritus
(5th – 4th century BC)
ATOMISM
Aristotle
(4th – 5th century BC)
CONTINUOUS MATTER
FOUR ELEMENTS – Earth, Air, Fire, Water
Boyle
(17th century)
Reintroduced ATOMISM in modern times.
Dalton
(19th century)
Atomic Theory to explain results of
EXPERIMENTS.
The Discovery of the Electron
The Discovery of the Nucleus
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The Discovery of the Nucleus
Expected Result:
Actual Result:
How small are Atoms?
A pebble is to Mt. Everest…
…As an atom is to a pebble.
It would take nearly ONE MILLION CARBON ATOMS, one after
another, to add up to the width of a human hair
Size of the Atom Vs. Size of the Nucleus
If a single ATOM were the
size of a football field…
NUCLEUS (center of atom)
In an atom: The majority of the
space is taken up by electrons
ELECTRON CLOUD
The NUCLEUS would be
the approximate size of a
FLEA on the 50 yard line
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Elementary Particles & the Standard Model of Physics
Mass Comparisons
(Neutral)
The electron is about 1800 times LESS massive than the proton (or neutron).
Electrons orbit the nucleus in orbital clouds; the degree to
which they spread out determines the overall size of the
atom.
The nucleus is composed of:
PROTONS
NEUTRONS
Volume Comparison
Mass Comparison
If the atom were the size of a
football field, the nucleus would be
the size of a flea on the 50 yard line
If the nucleus was as heavy as a
bowling ball, the electrons would
be as light as a penny.
The space occupied by the electrons
determines the size of the atom
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Rutherford’s model of the atom:
An atom is made up of a incredibly small, central, positively
charged nucleus, surrounded by even smaller, negatively charged
electrons that are moving around the atom.
NUCLEUS:
1) Subatomic particle: Core
of the atom.
2) POSITIVELY CHARGED.
3) Takes up very little space
in the atom.
4) Contains MAJORITY of
the mass of the atom.
(Figure is not to scale.)
Charged Particles:
The electrical charges on atoms DRASTICALLY influences the way
they behave
o The balance between positive
charges (protons) & negative
charges (electrons) determines the
on an atom.
What makes one Element different from another Element?
ELECTRICAL CHARGES RULE CHEMISTRY
• The identity of an element is determined by
the number of protons in the nucleus.
For example: any atom with 6 protons in the nucleus is a Carbon atom.
• The number of protons in the nucleus = atomic number (Z)
• Elements are arranged in the periodic table by their atomic number (Z)
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A Diversity of Elements:
Differences originating in the nucleus from varying numbers of protons
Elements are arranged in the periodic table by their atomic number (Z)
Counting numbers of Protons & Electrons
How many protons and electrons are in a Nitrogen (N)
ANION that has a -3 charge overall?
A. 7 protons & 7 electrons
B. 4 protons & 7 electrons
C. 7 protons & 4 electrons
D. 7 protons & 10 electrons
E. No enough information available to say
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