Download File

NOTES
2.2 The law of multiple proportions: when two elements form a sense of compounds,
the ratios of the masses of the second element that combine with 1 gram of the first
element can always be reduced to small whole numbers.
2.3 Dalton’s theory http://www.kentchemistry.com/links/AtomicStructure/dalton.htm
Dalton's Model of the Atom
Before we can discuss Dalton's Model of the atom, I must first mention the
Law of Multiple Proportions. Simply put, when elements combine to form
compounds they do so in whole number ratios.
Carbon and Oxygen can form either CO ( a 1:1 ratio) or CO2 (a 1:2 ratio). It
also states that if the mass of the first element is constant the second
elements masses would be in a whole number ratio.
1.00g of Carbon will have combined with 1.33g in CO
1.00g of Carbon will have combined with 2.66g in CO2
The mass are in a 1:2 ratio
Simply put if combinations are in whole number ratios, there must be a one.
This one being an atom. Here are Dalton's assumptions.
All matter is composed of atoms
Atoms cannot be made or destroyed
All atoms of the same element are identical
Different elements have different types of atoms
Chemical reactions occur when atoms are rearranged
Compounds are formed from atoms of the constituent elements.
2.4 J.J Thomson http://www.kentchemistry.com/links/AtomicStructure/JJThompson.htm
When investigating cathode rays using a highly evacuated discharge tube he
was able to use the calculated velocity and deflection of the beam to calculate
the ratio of electric charge to mass of the cathode ray. This was found to be
constant regardless of the gas used in the tube and the metal of the cathode
and was approximately 1000 times less than the value calculated for hydrogen
ions in the electrolysis of liquids. The electron is discovered, J J Thomson
publishes his discovery of a subatomic particle common to all matter.
The New Model of the Atom-Thompson knew
atoms were neutral, so there must be a balance
of negative and positive particles. This new
model is referred to as the Plum Pudding Model.
THERE IS A GREAT VIDEO ABOUT IT THAT CAN HELP YOU UNDERSTANDING
Millikan http://www.kentchemistry.com/links/AtomicStructure/Millikan.htm
The oil drop experiment was an experiment performed by Robert Millikan
and Harvey Fletcher in 1909 to measure the elementary electric charge (the
charge of the electron).
The experiment entailed balancing the downward gravitational force with
the upward buoyant and electric forces on tiny charged droplets of oil
suspended between two metal electrodes. Since the density of the oil was
known, the droplets' masses, and therefore their gravitational and buoyant
forces, could be determined from their observed radii. Using a known
electric field, Millikan and Fletcher could determine the charge on oil
droplets in mechanical equilibrium. By repeating the experiment for many
droplets, they confirmed that the charges were all multiples of some
fundamental value, and calculated it to be 1.5924×10−19 C, within one
percent of the currently accepted value of 1.602176487×10−19 C. They
proposed that this was the charge of a single electron.
With this data and J.J. Thompsons charge to mass ratio the mass of the
electron could be calculated.
1.5924×10−19 C
1 gram
x
-28
1.76 x 108 C
= 9.04 x 10
g or 9.04 x 10
-31
the accepted
kg value is 9.109 x
10-31 kg
CHENK OUT THE VIDEO ON LINE TO GET CLEAR!
Rutherford
http://www.kentchemistry.com/links/AtomicStructure/RutherfordTutorial.htm
Rutherford's Gold Foil Experiment Tutorial
The experiment to probe the structure of the atom performed by Hans
Geiger (Geiger counter) and Ernest Marsden in 1909, under the direction of
Ernest Rutherford at the Physical Laboratories of the University of
Manchester.
The Experiment
A beam of alpha particles, generated by the radioactive decay of radium,
was directed onto a sheet of very thin gold foil.
The gold foil was surrounded by a circular sheet of zinc sulfide (ZnS)
which was used as a detector: The ZnS sheet would light up when hit with
alpha particles.
THESE THEORIES NEED TO BE MEMORIZED COULD BE ON MULTIPLE CHOICE
2.5 the nucleus is assumed to contain protons, which have a positive charge equal in
magnitude to the electron’s negative charge, and neutrons which have virtually the
same mass as a proton but no charge. PICTURE
2.8 Formulas from names
Acids
PropertiesProduce H+ (H3O+) in water as the only positive ion.
Acids are electrolytes. They ionize and conduct electricity in water. ex.
HCl(aq)
Dilute quantities taste sour. ex. Citric Acid
Corrodes metals to produce hydrogen gas (H2)
Concentrated Acids are CAUSTIC, they cause chemical burns to skin.
Turn Blue Litmus Red
Phenolphthalein turn colorless
Neutralizes Bases
pH less than 7
CHECK THIS OUT
http://link.brightcove.com/services/player/bcpid1155269983?bctid=1405310652
http://link.brightcove.com/services/player/bcpid1155269983?bctid=1396941707
http://link.brightcove.com/services/player/bcpid1155269983?bctid=1396937749
Proton (p+) is positively charged particle of the atomic nucleus. The atomic number of
an element represents the number of protons in the nucleus.
Electron (e-) is negatively charged particle that can occupy a volume of space (orbital)
around an atomic nucleus. All atoms of an element have the same number of electrons
(i.e. any Chlorine atom is going to have 17 electrons). Electrons can be shared or
transferred among atoms.
Atoms have an equal number of protons and
electrons; therefore, they have a no net charge.
Ion is an atom that has gained or lost one or more electrons, thus becoming positively
or negatively charged.
Neutron is an uncharged particle of the nucleus of all atoms EXCEPT hydrogen. For a
given element, the mass number is the number of protons and neutrons (nucleons) in
the nucleus.
Isotope is one of two or more forms of atoms of an element that differ in their number
of neutrons. They have the same atomic number (same number of protons and
electrons), but a different mass number due to more or fewer neutrons.
Particle
Relative
Charge
Charge**
Mass
Relative
mass**
Location
1.672
Proton
+1.60 x 10
-19
C
+1
x 1024
Electron
-1.60 x 10
C
-1
-
x 10
28
nucleus
g
9.05
-19
1 amu
g
0 amu
~(1/1840
amu)
electron cloud
(orbital)
1.674
Neutron
neutral
0
x 1024
1 amu
nucleus
g
**Using relative charges and masses are used to keep calculations simple.
Atomic Number
The atomic number is the number of protons in the nucleus of an atom. It is
listed on the periodic table for each element. No two elements have the same
atomic number (or the same number of protons), so the atomic number identifies
the element.(symbol: Z)
Mass Number
Mass number: (symbol: A) total number of protons and neutrons in the nucleus
(not listed on the periodic table, since it varies).
NOTE this number is a whole number. Atomic Mass is different.
Atoms of the same element have the same atomic number, but may have
different mass numbers.
Isotopic notation for a particular atom (also called nuclide symbol notation):
A
E
Z
(E = element's symbol; A = mass number; Z = atomic number)
For example:
23
11
Na
Represents a sodium atom which always has 11 protons and in this case has a
mass number of 23.
(Note: This means that there are 12 neutrons. 23 - 11 = 12)
Mass number - atomic number = # neutrons
Determining the number of electronsThe number of electrons in an element can change. For a neutral atom, the number of
protons is exactly equal to the number of electrons. So the number of electrons is the
same as the atomic number. However, it is possible to remove electrons and not change
the identity of an element. These are called ions. The charge on the ion tells you the
number of electrons.
If the charge is positive, subtract that number from the atomic number to get the
number of electrons. You have more protons.
If the charge is negative, add the amount of charge to the atomic number to get the
number of electrons. You have more electrons.
Determine the number of protons, neutrons, and electrons
present in each of the following atoms.
(mass # = top number, atomic # = bottom number)
a)
28
a
14Si
electrons
protons = 14,
=
14,
neutrons = 14
b) 197
b
79Au
c)
n = 118
40
c
18Ar
d)
d p = 29, e = 29, n
29Cu
= 35
39
e p = 19, e = 19, n
19K
f)
p = 18, e = 18,
n = 22
64
e)
p = 79, e = 79,
= 20
133
f
p = 55, e = 55, n
= 78
55Cs
Identify atoms that are isotopes in each of the following sets of four
atoms.
A)
80
X
35
82
35
81
X
36
X
A
80
35
X
82
35
X
B)
19
19
X
9
C)
10
17
X
23
X
D)
70
33
X
X 8X
11
70
34
X
19
B
17
X
9
24
11
20
X
9
9
25
X
11
X
70
70
31
X32X
C
all
D
none
W tThe symbol, atomic number and atomic mass for the atoms with the
following characteristics.
1.
1. Contains 15 neutrons and 13 protons.
2.
3.
4.
33?
9. Copper that lost 2 electrons and has 30 neutrons.
10. Hydrogen that has 2 neutrons and no electrons.
75
As
58
Fe
26
5.
5. Rubidium that contains 87 nucleons.
8. An atom with number of neutrons 15 and mass number
Nb
33
d) 4. Iron contains 84 subatomic particles.
18 electrons?
93
41
c) 3. Contains 33 electrons and 42 neutrons.
7. An ion with atomic number 16, mass number of 32 and
Al
13
b) 2. Atomic number is 41. Neutrons 52.
6. An ion with 17 protons, 18 neutrons and 18 electrons?
28
87
Rb
37
6.
35
17
7. 32
16
8. 33
18
9. 59
29
10. 3
1
Cl
S
1-
2-
Ar
Cu
H
2+
+