http://teachers.yourhomework.com/blowe/1 today's agenda.w 1/19/11 recall 1 & 2 get your...
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http://teachers.yourhomework.com/blowe/ 1
Today's Agenda .w 1/19/11Recall 1 & 2
Get your comp books out before the bell rings
Continue Semester Review
Start studying for the Chem department final which will be on Monday January 24, 2011. There will be another class final as well.
Make sure to have a good book to read and pass time.
04/20/23
Chemistry Department Final
The Chemitry department final is on Monday January 24th. This will be closed notes and book.
There will be an additional Chem test on your “final” day based on material this semester. This one will be open notes and book.
04/20/23
Recall 1
Convert the following numbers into scientific notation
①7654
②0.000452
③5754.32
④0.08999
04/20/23
7.654 x 103
4.52 x 10-4
5.75432 x 103
8.999 x 10-2
Recall 2
Convert the following numbers from scientific notation to standard form
①9.99 x 102
②3.156 x 10-3
③7.23 x 105
④3.6 x 10-2
04/20/23
999
0.003156
723000
0.036
Temperature Conversions
To Fahrenheit from Celsius
F = C x (9/5) + 32
Example:
What is 32°C in °F?
F = 32 x (9/5) + 32
F = 57.6 + 32
F = 89.6°F
To Celsius from Fahrenheit
C = (F - 32) x (5/9)
Example:
What is 75°F in °C?
C = (75 - 32) x (5/9)
C = (43) x (5/9)
C = 23.9°C04/20/23
Temperature Conversionsto Kelvin
To Kelvin from Celsius
K = C + 273
Example:
What is 32°C in K?
K = 32 + 273
K = 305 K
To Celsius from Kelven
C = K - 273
Example:
What is 50 K in °C?
C = 50 – 273
C = -223°C
04/20/23Always change from Fahrenheit to Celsius then to Kelvin
Dimensional analysisVolume = How much space something takes up
Mass = How much something weighs
Density = Mass/Volume
Example:
A block of Aluminum is 3 cm x 4 cm x 5 cm and has the density of 2.7 g/cm3. What is the mass of this block?
Volume is 3 x 4 x 5 = 60 cm3
Mass = Density x volume
Mass = 2.7 g/cm3 x 60 cm3 = 162 g
Dimensional analysisGraduated cylinders can be used to find the
volume of an object.
Volume = Final measurement – Initial measurement
Example:
A graduated cylinder first measures 40 mL. After an object is dropped in it then reads 62 mL. What is the volume of the object?
V= 62 – 40 = 22 mL
BTW mL = cm3
Protons, neutrons, & electrons
Protons are positively charged particles in the center of atoms (p+)
The number of protons an atom has equals the Atomic Number of an Atom.
This is the top number on a periodic table
Ex: How many protons does Scandium have?
21
Elecrtrons are negativily charged particles that orbit the nucleus of an atom (e-)
The number of electrons equals the number number of protons in a neutral atom
When an atom has an extra electron(s), there is a negative net charge of an Atom
Ex: F1-, has one extra electron
Ex: Mg2+ has two missing electrons
04/20/23
Protons, neutrons, & electrons
Neutrons have no charge and are about the same size as protons. They are in the nucleus of an atom
The number of neutrons is the given atomic weight minus the atomic number.
Ex: A sample of Carbon is 14 amu (atomic mass units). How many neutrons are present?
14-12=
2 neutrons
pp
04/20/23
Atomic Structures SymbolsHydrogen
HNumber of Protons
Atomic mass
1 – 1 = 0 neutrons
H1
1
How many neutrons in this atom?
-EX-
-example-
Bk250
97How many neutrons in this atom?
250 – 97 = 153 Neutrons
Berkelium
The Bohr Model
• Niels Henrik David Bohr came up with the Bohr Model
• The Bohr Model looks like a mini solar system with the nucleus as the sun and electrons as planets.
Hydrogen Bohr Model
The Bohr Model
• Electrons orbit the nucleus in different levels.
• The first level is the closest to the nucleus and it can only hold 2 electrons.
• The second and third come after the first and are farther away, they can hold 8 electrons each.
• The 4th orbit can hold 18 electrons
18
8
82
Bohr example
11 Atomic Number
•Therefore I know this atom has 11 protons and because it’s neutral, 11 electrons
Sodium
11p•There are 12 neutrons because the Atomic Mass 22.99 rounded up to 23 (which you look up on your periodic table) minus the atomic number 11 equals 12
12n
2e
8e
1e
1st Orbital Shell
2nd
3rd
Average Atomic Mass
• Remember, isotopes are atoms with different numbers of neutrons
• Average Atomic mass = (mass) (abundance) + (mass) (abundance) +….
• Average Atomic mass = (mass) (%) + (mass) (%) +….
• You have to change % into decimalsi.e. 89.5% = .895 i.e. 12.4% = .124 i.e. 7% = .07
Example
• There are two isotopes of chlorine:chorine-35 (75.8%) and chorine-37 (24.2%)
a) How many neutrons does each isotope have? (Chorine has a atomic number of 17)
Chorine-35 has 18 neutrons
35 – 17 = 18 neutrons
Chorine-37 has 20 neutrons
37 – 17 = 20 neutrons
Example continued
• b) What is the average atomic mass of chlorine? (chorine-35 (75.8%) and chorine-37 (24.2%))
•Average Atomic mass = (mass) (%) + (mass) (%) +….
•Average Atomic mass = (35) (.758) + (37) (.242) = 26.53 + 8.95 = 35.48
Writing the Notation!
Write the electron configuration for the atom with atomic number 20
Ca has atomic number 20 (from the periodic table). 20 protons means there's 20 electrons.
The order of orbitals are:1s 2s 2p 3s 3p 4s 3d 4p
1s 2s 2p 3s 3p 4s 3d 4p2 2 6 62 2
You can check that we got 20 electrons
HomeworkBegin to start reviewing for the semester final
Some strategies that may help:
• Read over your notebook
• Try and find the chapters in the book that correspond to your notes and practice questions.
• Go over recalls and examples in your notebook
• Take time to memorize names like the difference between Nitrate and Nitride!
http://teachers.yourhomework.com/blowe/ 2004/20/23