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Atomic Structure. Standards. 1a. Students know how to relate the position of an element in the periodic table to its atomic number and atomic mass. 1b. Students know how to use the periodic table to identify metals, semi-metals {metalloids}, non-metals, and halogens - PowerPoint PPT Presentation
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Standards1a. Students know how to relate the
position of an element in the periodic table to its atomic number and atomic mass.
1b. Students know how to use the periodic table to identify metals, semi-metals {metalloids}, non-metals, and halogens
1e. Students know the nucleus of the atom is much smaller than the atom yet contains most of its mass.
Purpose We will use this information to build our
chemistry knowledge.We will use this information as the
foundation to calculate limiting reagent problems.
The standardized exams in the spring will test you on this information.
ObjectivesKnow the 3 particles of the atom and
where they resideKnow the difference between atomic
number and mass numberKnow how to write nuclide symbolsKnow the three isotopes of hydrogenKnow how to calculate atomic massKnow how to calculate percent abundance
First Some Questions…What are atoms made up of?
Protons, Neutrons and ElectronsWhere do you find these particles?
Protons and Neutrons are located in the nucleus
Electrons are located in the outer rings, outside the nucleus.
VocabularyAtom- from the Greek atomos=indivisible. The
atom is the smallest particle of an element that retains the properties of that element.
Nucleus: the center of the atom; composed of neutrons and protons. Because the mass of the proton and the neutron is much larger than that of electrons, almost all the mass is located in the nucleus.
Ion: a charged particle; # protons ≠ # electronsElectrons occupy most of the volume of an atom
outside/around the nucleus.
Fundamental ParticlesProton
A positively charged particle located in the nucleus.
NeutronA neutral particle located in the nucleus.
ElectronA negatively charged particle located outside
the nucleus.
Animation of the Atomhttp://vvsd.schoolwires.net/2349201028132033980/lib/
2349201028132033980/atom_animated.gifhttp://vvsd.schoolwires.net/2349201028132033980/lib/
2349201028132033980/atom_animated.gif
http://www.google.com/imgres?imgurl=http://members.shaw.ca/len92/atom_animated.gif&imgrefurl=http://members.shaw.ca/vict/electricity_intro.htm&h=260&w=270&sz=6&tbnid=tAjDJsPzhGAxvM:&tbnh=95&tbnw=99&zoom=1&usg=__8fyNMhCgDiqyFH3eSESGT0PZS2o=&docid=gQA81nwMuwx71M&sa=X&ei=ElBlUpyKFYP_igLhlIGwBg&ved=0CDgQ9QEwBA
QuestionWhat differentiates one atom from another
atom?
The number of PROTONS
Atomic Number (Z)Number of protons in the nucleus of an
atomThis number is found on the Periodic
TableAtomic Number identifies an elementAlways a positive number (b/c it is a
counting #)Tells number of electrons in a neutral
atomAn atom is electrically neutral
ElAZ
What does it mean to be electrically neutral?The atom has no chargeThe number of protons = the number of
electrons
QuestionWhat observations can you make about
atomic numbers on the periodic table?
Atomic Number increases as you go across the rows from left to right.
QuestionsWhat is the atomic number of Chlorine?
What can you tell me about its protons and electrons?
What element has 20 protons?What is the relationship between the #
protons and the atomic number? They’re equal.
Complete the ChartElement Symbol Atomic # # Protons
Potassium
5
16
Y
K 19 19
Boron B 5
Sulfur S 16
Yttrium 39 39
Atomic Structure of Potassium
Mass Number (A) Total number of protons and neutrons
in the nucleus of an atomAlways a positive numberYou can determine the nuclear
composition of an atom from its mass number and atomic number
ElAZ
QuestionWhat do the atomic number and the mass
number have in common? Both Positive integersBoth have the same # of protons
How to find # of Neutrons Mass # - Atomic#= # Neutrons
Or
# protons + # neutrons= Mass # (atomic number + # neutrons)=Mass #
Complete the ChartAtomic# Mass# #Protons #Neutro
ns#Electrons
Chemical Symbol
9 10
14 15
47 22
55 25
6 C
19 9 9 F
14 29 14 Si
22 22 25 Ti
25 30 25 Mn
6 12 6 6
IsotopesAtoms of the same element with differing
numbers of neutronsAtoms with the same atomic number but
different mass numberIsotopes of an element have different massesChemical properties of different isotopes are
virtually the same
Nuclide Symbol
A=Mass #Z= Atomic #
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NuclideA specific kind of atomSpecification of an element in terms
of its nuclear composition/structureTells number of protons and number
of neutrons
# protons # neutrons # electrons
Chemical Symbol
C 6 [6, 7, 8] 6
Nuclide Symbol 6 7 6C136
Complete the ChartAtomic# Mass# #Protons #Neutro
ns#Electrons
Chemical Symbol
9 10
14 15
47 22
55 25
6 C
19 9 9 F
14 29 14 Si
22 22 25 Ti
25 30 25 Mn
6 12 6 6
Nuclide Symbol
F199
Si2914
Ti4722
Mn5525
C126
3 Isotopes of Hydrogen
Isotope OfHydrogen
Nuclide Symbol
# protons # neutrons # electrons
H11
H31
H21Deuterium 1 1 1
Protium 1 0 1
Tritium 1 2 1
NuclidesBy specifying the nuclear structure, then you
call it a nuclide. But if you say Carbon atom, you do not know
which Carbon atom it is, therefore you don’t know how many neutrons it has
Example: Brothers and Sisters-You are members of the Jones family, but you
have not specified which Jones member you are referring to. If you say Jimmy Jones, then we know exactly which member you are referring to. Just like when you say carbon-13, we know exactly which kind of carbon atom, the one 7 neutrons in the nucleus.
Write the nuclide name and nuclide symbol #
protons
# neutrons
# electrons
Nuclide Name
Nuclide Symbol
17 20 18
20 20 18
92 146 92
Chlorine-37Anion
Cl3717
24020Ca
U23892
Calcium-40Cation
Uranium-238
Atomic MassA weighted average of the atoms in a
naturally occurring sample of the element.Naturally occurring: no matter where you
get the sample from, it will have the same percentages of isotopes.
Construct a Fruit BasketFruit Type Weight of Each Piece
2 grapefruit 14 oz4 apples 10 oz3 pears 7 oz1 kiwi 3 oz
What is the Average Weight?
Fruit BasketAverage weight=9.2oz
Each type of fruit makes a different contribution to the overall weight
How many pieces of fruit actually weigh 9.2 ounces? None!
What does 9.2 oz mean? Fictitious non-existent piece of fruit
Atomic MassIf you have a recipe, you could count items
to put in, say 200 chocolate chips, 3 eggs, etc.
But suppose I have a recipe to make a compound. I need 100 hydrogen atoms and 50 oxygen
atoms-you cannot count atoms or pluck them out with atomic tweezers!
So instead they are massed. Careful here, the mass of an object is completely
different from the weight of an object.
QuestionWhat accounts for the mass of the atom?
# protons & # neutrons in the nucleus
Atomic MassKnow that 1.0 amu is defined as
exactly 1/12 the mass of a atom.Carbon-12 has 6 protons and 6
neutrons, therefore 1 proton or 1 neutron = ~1 amu
1 amu = 1.6606 x 10 -24 gramsSince the mass mostly depends on #
protons and # neutrons, you’d think atomic mass would be a whole number, but it isn’t. How come?
C126
Atomic Mass In nature, most elements exist as a mixture of 2 or more
isotopes. Each isotope of an element has a fixed, constant mass and
fixed constant relative abundance.Relative abundance-
The amount (%) of the isotope present in a sample of the element
Sample of carbon from anywhere in the world; coal from S. Africa, W. Virginia or Pennsylvania → 99% C-12 and 1% C-13
Atomic Mass on the periodic table takes into account the larger and smaller masses of the isotopes
→ Idea of weighted average
Calculating Atomic MassTo calculate atomic mass you need to know 3
things:# of stable isotopesMass of each isotope% abundance of each isotope
Example: Chlorine Calculationmass of isotope X relative abundance + mass of isotope X relative abundance
=_______amu
(34.969)(.7577) + (36.935)(.2423) = That’s the same value on the periodic
table!
Isotope Mass of Isotope Relative Abundance Atomic Mass
Cl-35 34.969 75.77%
Cl-37 36.935 24.23%
35.45 amu
QuestionHow many chlorine atoms actually have a
mass of 35.45 amu? NONE
So the atomic mass, in amu, is the average of a fictitious non-existent atom of an element.
Example: Copper CalculationIsotope Mass of Isotope Relative Abundance Atomic Mass
Cu-63 62.9298amu 69.09%
Cu-65 64.9278 30.91%
(62.9298)(.6909)+(64.9278)(.3091)=63.5464 amu
Calculating Relative AbundanceTo Calculate % Abundance:
Make a ChartIsotopic Mass x % Abundance of each
isotopeSet-up equationSolve for “x” Plug in “x” value to solve for “y”
ExampleIsotope Mass of Isotope Relative Abundance Atomic Mass
B-10 10.013
B-11 11.009
1.00x + y = 1.00y = 1 – x
10.013 (x) + 11.009 (1 –x) = 10.811
10.013x + 11.009 -11.009x = 10.811
-0.996x = -0.198x = .1987
y= 1-.1987 y= .8013
B-10 = 19.87%
B-11 = 80.13%
x
1- x
The End