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Lecture 5 9/9/05
Quiz 2
1. Which of the following has the highest temperature?
30 °C 80 °F 300 K
2. How many protons and neutrons does an atom of potassium-40 have?
F32)F(TF9
C5)C(T C15.273)C(T)K(T
1 mole =the amount of substance that contains as many particles (atoms, molecules) as there are in 12.0 g of 12C.
1 mole =the amount of substance that contains as many particles (atoms, molecules) as there are in 12.0 g of 12C.
THE MOLE
1 mole = 6.02214199 x 1023 particles = Avagadro’s number
MOLAR MASS
sum of the atomic weights of all atoms in the
molecule molecular weight in grams/mole
1 mol of 12C = 12.00 g of C = 6.022 x 1023 atoms of C
12.00 g/mol is the molar mass of 12C
12.011 g/mol is the molar mass of carbon (taking into account all of the isotopes of C)
Mass to Moles
gramsmole 1
gramsMoles
mole 1/grams
gramsMoles
mass Molar
MassMoles
How many moles of Mg is represented by 0.200 g? How many atoms?
How many moles of Mg is represented by 0.200 g? How many atoms?
Mg has a molar mass of 24.3050 g/mol.
0.200 g • 1 mol
24.31 g = 8.23 x 10-3 mol
8.23 x 10-3 mol • 6.022 x 1023 atoms
1 mol
= 4.95 x 1021 atoms Mg
How many atoms in this piece of Mg?
Dmitri Mendeleev (mid-19th cen)Periodic Table
Lined up elements in horizontal rows with increasing atomic weight
Started new rows when properties seemed similar
Left space in table where he predicted new elements would be discovered
HGJ Moseley (1913)Discovered a method to determine atomic
numberRealized Periodic Table should be organized
by atomic number
Law of Chemical Periodicity:Properties are periodic functions of atomic #
Periodic Table
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