Atom Atomos A tomos un + cut · 2010-07-02 · 1 ©Prof. Zvi C. Koren 21.10.07 2 אשונ...
Transcript of Atom Atomos A tomos un + cut · 2010-07-02 · 1 ©Prof. Zvi C. Koren 21.10.07 2 אשונ...
1 ©Prof. Zvi C. Koren 21.10.07
2נושא
ומולים, איזוטופים, אטומים
Atom Atomos A + tomos
un + cut
2 ©Prof. Zvi C. Koren 21.10.07
3 ©Prof. Zvi C. Koren 21.10.07
amu = atomic mass unit
Atomic Composition
e–
H+
Relative Atomic Mass Scale:
Mass of 1 atom of 12C 12 (exactly) amu
4 ©Prof. Zvi C. Koren 21.10.07
Atomic Symbols & Isotopes (איזוטופים)
XA
ZElement symbol
Atomic Number# of protons =
Mass Number# of protons + # of neutrons =
Examples of Isotopes:
C14
6 C
13
6 C
12
6 :carbonelement theof isotopes Three
for a neutral atom: # of electrons = # of protons
protium deuterium (D) tritium (T)
Isotopes = different atoms of the same elementRadioactive
Consider ions (charged species – “to go”):13C4-: #p = __, #n = __, #e = __. 3H+: #p = __, #n = __, #e = __.
carbon-12 carbon-13 carbon-14#p =
#n =
#e =
#p =
#n =
#e =
1H 2H 3HThree isotopes of the element hydrogen:
5 ©Prof. Zvi C. Koren 21.10.07
Atomic Mass or Atomic Weight (A.W.)
the weighted average of all the stable isotopes of that element
Atomic Mass or
Atomic Weight (amu)
Percent (%)
AbundanceMass (amu)
Mass
NumberSymbolElement
1.0079799.98551.0078251
HHydrogen0.01452.0141022
10.81119.9110.01293910
BBoron80.0911.00930511
15.9994
99.75915.99491416
OOxygen 0.037416.99913417
0.203917.99916018
12.011
12
(exactly)12
CCarbon
13
Table of Exact Masses of the Stable Isotopes of Some Elements
For example:
A.W. of O = 0.99759(15.994914) + 0.000374(16.999134) + 0.002039(17.999160)
= 15.9994 amu [This is the mass that appears in the Periodic Table.]
?
6 ©Prof. Zvi C. Koren 21.10.07
Notes about Atomic Weights
• All atomic masses (except for 12C) are NOT integers
• Mass number is always an integer!
• A.W. the sum of all the particles.
For example for deuterium, 2H (or D):
1 proton = 1.007276 amu
1 neutron = 1.008665
1 electron = 0.0005485799
Total mass of particles = 2.0164895799 amu
Atomic Weight = 2.014102 amu
Difference in mass = 0.002387 amu = 3.9638x10-30 kg
Why?
Mass defect: E = mc2 = (3.9638x10-30 kg)(2.997925x108 m/s)2 = 3.5625x10-13 J/atom
1 atom = 2.014102 amu = 3.3445x10-24 g
energy/gram = 1.0652x1011 J/g = 1.0652x108 kJ/g
energy/mole = 2.1454x108 kJ/mole
For exothermic chemical reactions: energy/mole 102 kJ/mole
7 ©Prof. Zvi C. Koren 21.10.07
1A
H
Li
Na
K
Rb
Cs
Fr
Chemical Periodicity
Li
Na
K
M(s) + H2O(l) MOH(aq) + ½H2(g) + Heat
Reaction Names:
Hydrolysis
Single Replacement
“Redox”
Exothermic
Gas-Forming
aqueous
Elements of the same group have similar – but not identical – properties.
8 ©Prof. Zvi C. Koren 21.10.07
mole
Mole Day is celebrated on Oct. 23 from 6:02 am to 6:02 pm
9 ©Prof. Zvi C. Koren 21.10.07
Lorenzo Romano Amadeo CarloAvogadro1776 – 1856
The word “mole”:
Coined by Wilhelm Ostwald (1896), Latin “moles” meaning “heap” or “pile”.
Avogadro’s Number:
1 mole of things = 6.022x1023 things
10 ©Prof. Zvi C. Koren 21.10.07
The mole is a number!
For example:
1 dozen = 12
1 dozen eggs = 12 eggs
1 dozen chairs = 12 chairs
1 dozen molecules = 12 molecules
1 dozen atoms = 12 atoms
1 mole = 6.022x1023
1 mole of eggs = 6.022x1023 eggs
1 mole of chairs = 6.022x1023 chairs
1 mole of molecules = 6.022x1023 molecules
1 mole of atoms = 6.022x1023 atoms
The Mole … once agin … The Bridge to the Human Scale
11 ©Prof. Zvi C. Koren 21.10.07
What’s so great about the mole or Avogadro’s Number???
Converts masses in amu to the same number in grams
Molar Mass
(g/mol)MassesAtoms/Molecules
12 g/mol
12 amu
12 g
1 12C atom
1 mol of 12C atoms
10.0129 g/mol
10.0129 amu
10.0129 g
1 10B atom
1 mol of 10B atoms
32.00 g/mol
32.00 amu
32.00 g
1 O2 molecule
1 mol of O2 molecules
2.00 g/mol
2.00 amu
2.00 g
1 H2 molecule
1 mol of H2 molecules
Molecular Weight (MW)
Formula Weight (FW)
1 g = 6.022x1023 amu
g ? amu
Avogadro’s Number is a Magic Number!!!
Atomic Weight (AW)
12 ©Prof. Zvi C. Koren 21.10.07
1 g = 6.022x1023 amu
g amu
5.0 g amu = ?
5.0 g gamu
1= 3.0 x 1024 amu
“Unit Factor”
Mass Conversions
6.022 x 1023
Example for g amu:
2.0 amu g = ?
2.0 amug
amu1 = 3.3 x 10-24 g
“Unit Factor”
6.022 x 1023
Example for amu g:
13 ©Prof. Zvi C. Koren 21.10.07
Grams Moles31.8 g Cu Moles of Cu atoms = ?
31.8 g Cug Cu
mol Cu1
63.55= 0.500 mol Cu
Moles Grams
“Unit Factor”
(A.W.)
0.300 mol Cu atoms g Cu = ?
g Cu
mol Cu1
63.55= 19.1 g Cu
“Unit Factor”
(A.W.)
0.300 mol Cu
Moles and Molar Masses of the Elements
14 ©Prof. Zvi C. Koren 21.10.07
How many moles are there in 1.00 lb of silicon?
Weight
1.00 lb Sig
lb1
453.6 molg28.0855
1= 16.2 mol Si
Moles
Grams MolesWeight
15 ©Prof. Zvi C. Koren 21.10.07
Grams Moles1.6 g CH4 Moles of CH4 molecules = ?
1.6 g CH4g CH4
mol CH41
16.0= 0.10 mol CH4
Moles Grams
“Unit Factor” (M.W.)
0.10 mol CH4 molecules g CH4 = ?
g CH4
mol CH41
16.0= 1.6 g CH4
“Unit Factor” (M.W.)
0.10 mol CH4
Molar Mass or Molecular Weight (M.W.)For Example, for CH4: MW = 12.0 + 4(1.0) = 16.0 g/mol
Also:
M
mn
16 ©Prof. Zvi C. Koren 21.10.07
Moles Number
Number of Items
0.20 mol tables # of tables = ?
0.20 mol tablesmol tables
tables6.02x1023
1= 1.2x1023 tables
Number Moles
“Unit Factor”
1.2x1023 Cu atoms mol Cu = ?
mol Cu atoms
Cu atoms6.02x1023
1= 0.20 mol Cu atoms
“Unit Factor”
1.2x1023 Cu atoms
Avogadro’s Number:
1 mole of things = 6.022x1023 things
17 ©Prof. Zvi C. Koren 21.10.07
Summary
MoleAvogadro’s
NumberMass
constantvariable