Download Atom - Perry Local Schools

Wednesday, October 3rd
Bellwork: What information can be used for identifying where you live? How are YOU identified?
Power of the mind and intellectual thought were the
primary avenues to the truth.
Curiosity sparked the interest of scholarly thinkers known
as philosophers who considered many of life's mysteries.
As the speculated about the nature of matter, many
philosophers formed explanations based on their
own life experiences.
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Democritus
-matter was made up of tiny individual
particles called atomos (we derive our
English word, atom) which move through
empty space
Aristotle
-rejected the idea of atoms (denied their
existence), he didn't believe empty space
could exist.
-matter is made of earth, fire, air, and
water
-because he was very influential people
rejected Democritus
-No one challenged him for 2,000+ years!
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Dalton
-could actually do experiments
-Created
Dalton's atomic theory
*matter is composed of extremely small
particles called
atoms
*atoms are divisible and indestructible
*atoms of a given element do not always have
the same properties and can have slightly
different masses
*atoms of a specific element are different
from those of another element
*different atoms combine in simple wholenumber ratios to form compounds
*in a chemical reaction, atoms are separated,
combined, or rearranged.
-conservation of mass
in chemical reactions is
the result of separation, combination, or
rearrangement of atoms (not created,
destroyed, or divided)
Atom-smallest particle of an element that retains the
properties of the element.
-idea of its size: world population = 6.5x109 in 2006.
The penny has 2.9x1022 atoms. (5 trillion times world
population!)
-They can be seen! You have to use a scanning
tunneling microscope (STM) to see individual atoms.
Once people were convinced that the atom existed -it led
to
more questions being asked just like all good experiments.
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-Scientists began to make connections between matter
and electric charge.
-Some wondered how electricity might behave in the
absence of matter.
-Used the newly invented vacuum pump to pass electricity
though glass tubes from which most of the air had been
removed.
-tubes are called cathode ray tubes. (positive end is
called anode, negative end is called cathode)
Note: anions are negative, and cations are positive­shows direction charges want to move.
Crooks
-saw a spark of green light when the
electricity struck zinc sulfide coating in the
tube (some sort of radiation was produced)
-Cathode ray was the name given to this spark
of light, this eventually led to the invention of
the tv.
-Conclusions: streams of charged particles
were passing through the tube, they
carried a negative charge.
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J.J. Thomson
-he concluded that the mass of the charged
particle was much less than the hydrogen atom,
the lightest known atom.
-This meant that there were particles
smaller than an atom.
-Dalton was incorrect!
-He had identified the first subatomic particle the electron
Millikan
-did oil drop experiment and determined the charge
of an electron.
-His setup was so good that it is within 1% of the
current accepted value!
-then knowing the charge and the known charge-tomass ratios, he calculated the mass of an electron
Two major questions were then asked: If electrons mass is
so small, what accounts for the rest of the mass in an
atom? & If an electron is negative, how is it that all
matter is neutral?
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J.J. Thomson proposed a model of the atom known as the
plum pudding model
-said there was positive charge throughout and that
negative electrons sat with in
-his model didn't last long.
Rutherford
-studied how positively charged particles interacted
with solid matter.
-conducted an experiment to see if alpha
particles would be deflected as they passed
through a thin piece of gold foil
-Hypothesis: it wouldn't alter the path of alpha
particles and that they would see slight altered
paths when collisions happened with an electron.
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Results: most past right through with no deflection,
some were deflected at large angles and some came
straight back.
-Kind of like firing a large artillery shell at a sheet
of paper and the shell coming back at the cannon!
Concluded:
-Plum pudding model was wrong,
-atom is mostly empty space through which electrons
move
-most of atom's positive charge and almost all of its
mass were contained in a tiny dense region in the
center of the atom-called the nucleus
-negative particles are held within the atom by their
attraction to positive nucleus
Nucleus is very dense. IF it was the size of the dot on an exclamation point mass would be as much as 70 automobiles! If its diameter was 2 football fields, nucleus would be the size of a nickel.
­Neutral Nature of Matter: the positive charge in the nucleus is balanced out by the negative electrons ­but didn't account for atomic mass.
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Proton­ carries an equal but opposite charge of an electron.
­Rutherford discovered it
Chadwick ­discovered that nucleus also has neutrons Neutron mass = mass of proton
Neutrons have NO CHARGE
Henry Moseley
­discovered atoms of each element contain a unique positive charge in the nuclei
­number of protons in an atom identifies the atom
­we call this atomic number
­The periodic table is organized left to right and top to bottom by increasing atomic number.
­All atoms are neutral; therefore, #p + = #e­
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Summary:
­All atoms are made up of 3 fundamental subatomic particles: protons, neutrons, and electrons
­Atoms are spherically shaped, small, dense nucleus of positive charge surrounded by negative charge (1 or more)
­Most of an atom is fast­moving electrons traveling through empty space that surrounds the nucleus.
­electrons are held by their attraction to positive charge in the nucleus
­nucleus contains protons and neutrons and they make up 99.97% of the mass of an atom.
­atom is neutral: #protons = # electrons
­Subatomic particles are made up of quarks
Thursday, October 4th
Bellwork: Complete the worksheet (front
and back) that you picked up for 4.1 and
4.2 as a way of reviewing all of the
history from yesterday.
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Homework: 4,6,7
4. Explain how Dalton's theory of the atom and the conservation of
mass are related.
Dalton explained that atoms are neither created nor destroyed in
chemical reactions, only rearranged.
6. Design a concept map that compares and contrasts the atomic
ideas proposed by Democritus and Dalton.
See next page.
7. Describe the structure of a typical atom. Identify where each
subatomic particle is located.
A typical atom consists of a central, small, dense nucleus containing
protons and neutrons. The nucleus is surrounded by a cloud of
negatively charged electrons.
8. Compare and Contrast Thomson's plum pudding atomic model with
Rutherford's nuclear atomic model.
Thomson's plum pudding model describes atoms as spherical
particles with uniformly distributed positive charge in which
individual, negatively charged electrons are located in fixed
positions. In contrast, Rutherford's model states that an atom is
mostly empty space, with a small, dense, central nucleus containing
all of an atom's positive charge and most of its mass. The
negatively charged electrons move through the empty space and are
held in the atom by their attraction to the positively charged
nucleus.
matter composed
of extremely
small particles
called atoms
all atoms of a given
element are
identical but differ
from the atoms of
other elements
Democritus
matter is composed of
empty space through
which atoms move
atoms could not
be created,
divided, or
destroyed
Dalton
different kinds of
atoms come in
different sizes and
shapes
different atoms
combine in simple
whole-number ratios
to form compounds
differing
properties of
atoms are due to
the size, shape,
and movement of
the atoms
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Refer back to Dalton's atomic theory:
­States that 'atoms of a given element do not always have the same properties and can have slightly different masses.'
­Number of neutrons can be different
­Atoms with the same number of protons but different numbers of neutrons are called isotopes.
­atoms with more neutrons have more mass
­Isotopes of same element all have the same chemical behavior.
­the number of electrons is the only thing that chemical behavior is dependent upon.
­Each isotope of an element is identified with a number called mass number.
Mass # = atomic number(# of protons) + neutrons
­Example: Copper­63, Copper­65
*remember: atomic number (protons) doesn't change!
­In nature elements are found as mixtures of isotopes. How much each isotope occurs in any given substance is constant
Due to mass of p +, no, and e ­ being so small chemist developed a method for measuring the mass of an atom relative to mass of a specific atomic standard.
­The standard is Carbon­12
­Carbon has exactly 12 amu so 1 amu = 1/12 the mass of a carbon­12 atom = almost the mass of one proton.
Atomic mass of an element is a weighted average of the isotopes of that element.
­Sometimes you can gain an understanding of which isotope may be more common if the amu (atomic mass unit) is close to a whole number it indicates that isotope is more common (not always)
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Use what you've learned to complete the
table below:
Element
Atomic
Number
Protons
Electrons
19
35
Ne
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ANSWERS
Element
Atomic
Number
Protons
Electrons
K
19
19
19
Br
35
35
35
Ne
10
10
10
12
Standard Notation: written as a way to express the chemical
symbol, the mass number, charge (if any), and the atomic
number(#of protons)
Examples:
Carbon-12
Carbon-13
Carbon-14
The three carbon molecules above represent isotopes.
Ion-Charged element, one that has either gained electrons
(become negative) or lost electrons (become positive).
Cu2+
Cl-
Ni3+
O2-
How do you know how many electrons are gained or lost?
Using what you know and have learned...try completing the table on atomic structure. You will want to use a periodic table. 13
Friday, October 5th
Bellwork pg 116: 12­15
12. How many protons and electrons are in each atom?
a. radon b. magnesium
a. 86p, 86e
b. 12p, 12e
13. An atom of an element contains 66 electrons.
Which element is it?
dysprosium
14. An atom of an element contains 14 protons.
Which element is it?
silicon
15. Do the atoms shown in the figure have the same atomic number?
yes, there are nine
With a person other than your lab partner: Complete Practice Problems 16­19, 21,23, 24
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16. Determine the number of protons, electrons, and neutrons for isotopes b­f in the table above. Name each isotope and write its symbol.
Element
Atomic Mass Protons &
Neutrons
Isotope
#
#
Electrons
Name
b. Calcium
20
46
20
26
Calcium-46
c. Oxygen
8
17
8
9
Oxygen-17
d. Iron
26
57
26
31
Iron-57
e. Zinc
30
64
30
34
Zinc-64
f. Mercury
80
204
80
124
Mercury-204
Symbol
17. An atom has a mass number of 55 . Its number of neutrons is the sum of its atomic number and five. How many protons, neutrons, and electrons does this atom have? What is the identity of this atom?
25 protons, 25 electrons, 30 neutrons. Manganese
18. Boron has two naturally occuring isotopes: boron-10 (19.8%
abundant, mass 10.013amu) and boron-11 (80.2% abundant, mass
11.009 amu) Calculate the atomic mass of boron. 10.81amu
19. Nitrogen has two naturally occurring isotopes, N-14 and N-15.
Its atomic mass is 14.007. Which isotope is more abundant?
Explain your answer.
N-14 is most likely more abundant because the atomic mass is
closer to 14 than 15.
21. Which subatomic particle identifies an atom as that of a
particular element? the proton
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23. Copper has two isotopes: Cu-63 (abundance 69.2%, mass =
62.930 amu). Cu-65 (abundance 30.8%, mass = 64.928 amu).
Calculate the atomic mass of copper. 63.5amu
24. Three magnesium isotopes have atomic masses and relative
abundances of 23.985amu (78.99%), 24.986anu (10.00%), and
25.982 (11.01%). Calculate the atomic mass of magnesium.
24.31amu
Complete the worksheets on atomic
structure and isotopes/average
atomic mass. -Finish for homework
-Snackium lab Prep-homework
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Tuesday, October 9th Bellwork
Refresh your memory, what is a chemical
reaction?
A chemical reaction is the change of
one or more substances into new
substances -this only involves the
electrons.
Nuclear Reaction- can change one element into
another element by creating a change in the
nucleus of the atom.
-We realized its existence in a process called
radioactivity where radiation was
spontaneously emitted.
Radiation- rays or particles emitted by
radioactive material.
Why do they emit radiation? -their nuclei are
unstable
-Unstable nuclei lose energy by emitting
radiation in a spontaneous process called
radioactive decay.
-the primary factor in determining an atom's
stability is its ratio of neutrons to protons
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3 types of radiation-based on their electrical charge.
alpha particles (2p+, 2no) = 2+ charge
-Ernest Rutherford, an English scientist, discovered alpha
particles in 1899 while working with uranium.
-occur naturally in the environment in soils, rocks, and water
Uses of alpha particles:
*Radium-226 may be used to treat cancer, by inserting tiny
amounts of radium into the tumorous mass.
*Polonium-210 serves as a static eliminator in paper mills
and other industries. The alpha particles, due to their
positive charge, attract loose electrons, thus reducing
static charge.
*Some smoke detectors use the alpha emissions from
americium-241 to help create an electrical current.
beta particles (e­) = 1­ charge
­Henri Becquerel is credited with the discovery of beta particles. In 1900, he showed that beta particles were identical to electrons, which had recently been discovered by J. J. Thompson.
­energy can break chemical bonds and form ions.
­ used in medical diagnosis, imaging, and treatment
­harmful to cells and the environment
­people who have taken radioactive iodine will emit beta particles. ­Radioactive iodine may enter the environment during a nuclear reactor accident and find its way into the food chain.
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Gamma Rays - no mass, no charge, usually accompany
alpha or beta radiation, and they account for most energy
lost during decay.
-Henri Becquerel discovered them, shortly after x-rays
were discovered. He said uranium emitted similar invisible
light energy.
-Gamma photons have about 10,000 times as much
energy as the photons in the visible range of the
electromagnetic spectrum.
-They can pass through many kinds of materials,
including human tissue...lead is often used to help
shield us against them.
What's the difference between x-rays and gamma rays?
-Gamma rays originate in the nucleus. X-rays
originate in the electron fields surrounding the
nucleus or are machine-produced.
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