journal #11 how do you find the average age of the students in this classroom?
TRANSCRIPT
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Journal #11
• How do you find the average age of the students in this classroom?
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Current AtomicModel
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Subatomic Particles
Charge Mass Location
Proton +1 amu(1/12 of a carbon atom)
Nucleus
Neutron none 1 amu Nucleus
Electron - Almost0 amu
Outside nucleusIn motion
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IsotopesDistinguishing Atoms
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What makes an atom unique?
• Number of protons• Number of neutrons• Number of electrons
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The Atom
Almost every atom is neutral, a balance of positive & negative charges.
FYI: If the nucleus was the size of a pea it would have a mass 250 tons. If the nucleus was the size of a marble, the atom would be the size of a football stadium.
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atomic number = # of p+ & e-
• top number• # electrons = # protons (in a neutral atom)
• This number never changes• If it did you would make a different element
12.0107
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mass number
= # protons + # neutrons
This is NOT on the periodic table! You round the atomic mass to get the mass number of the most common isotope.
12.0107
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Try some
Pb Ag
Na C
How many protons, neutrons & electrons do each of the elements have?
Use the periodic table in the back of your book:
p+= 82
e-= 82
n= 207- 82= 125p+= 11
e-= 11
n= 23- 11= 12
p+= 6
e-= 6
n= 12- 6= 6
p+= 47
e-= 47
n= 108- 47= 61
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Stop and practice
Packet page 3
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Isotopes
• Different versions of an atom
• # protons is the same– Atomic number is the same
• # neutrons is different– Mass number is different
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Chemical Properties of Isotopes
• Chemically, all isotopes are the same since they all have the same number of electrons.
• Electrons determine the chemical properties of an element.
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Designating Isotopes
Mass # Symbol 14 CAtomic # 6
---------------------------------------------Hyphen notation:
Name – mass # carbon-14
Nuclear symbol:
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Practice
• How many protons, electrons and neutrons make up an atom of bromine-80?– 35 protons, 35 electrons, 45 neutrons
• Write the nuclear symbol for carbon-13– 13
6C
• Write the hyphen notation for the isotope with 15 electrons and 15 neutrons.– Phosphorus-30
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Try Some + worksheet
Atomic #
(p+/e-)
Mass #
(p+ + n)
# p+ # n symbol
9 10
14 15
47 25
55 25
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Check
Atomic # Mass # # p+ # n symbol
9 19 9 10 F
14 29 14 15 Si
22 47 22 25 Ti
25 55 25 30 Mn
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Stop and practice
• Do packet pages 9 & 10
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% abundance
• Most elements occur as mixtures of isotopes.• The % of each isotope that occurs for each
element is nearly always the same, no matter where the element is found.
• The percentage at which each element (ISOTOPE) occurs in nature is called the isotope’s % abundance.
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Why atomic mass is a decimal
• Average atomic mass is the weighted average mass of atoms in a naturally occurring setting
• To calculate (Isotope mass x % abundance)+ (Isotope mass x % abundance)= average atomic mass
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Calculating average atomic mass
• In order to calculate the average atomic mass, you need to know three things1. The number of isotopes
2. The mass of each isotope
3. The natural % abundance of each isotope
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Marble Example: You have 100 marbles; 60 black marbles (5g each), 40 red marbles (8 g each).
1) Find the % abundance of each marble isotope?
Marble type x 100 = % abundance Total marbles
60 black marbles x 100= 60% black marbles 100 marbles
40 red marbles x 100= 40 % red marbles 100 marbles
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2) What is the average mass of each marble? (Isotope mass x % abundance)
+ (Isotope mass x % abundance)
= average atomic mass
(5 g x 60% black marbles) 3.0g+ (4g x 40% red marbles) 1.6 g= average atomic mass 4.6 g
FYI: 60%= 60 /100=0.60
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Atomic Mass of Chlorine
Element % abundance Mass
Chlorine -35 75.77%(divide by 100)
34.969
Chlorine -37 24.23%(divide by 100)
36.966
Atomic Mass
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Atomic Mass of Chlorine
Element % abundance Mass
(amu)
Chlorine -35 75.77% x 34.969 = 26.496
Chlorine -37 24.23% x 36.966 = 8.957
Atomic Mass35.453
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Determine the Element
• 63X weighs 62.929601 amu and has a % abundance of 69.15%
• 65X weighs 64.927794 amu and has a % abundance of 30.85%
• Find the average atomic mass and then compare to the periodic table.
• What is the element?