Download Chem Ch4,25

Ch4.1 – Atomic Structure
History of the atom
Aristotle- Everything is made of a substance called “hyle.” Re-arrange hyle to make
different substances. Aristotle's philosophies accepted by Roman Catholic church
- Western science in dark ages until ~ 1500’s.
John Dalton (1800’s): Father of Atomic Theory.
1. Everything is made up of tiny, indestructible particles.
He called them atoms.
2. Pictured atoms as tiny, solid spheres.
3. All atoms of the same element are
identical atoms of different elements
are different.
4. Atoms of different elements combine
in whole number ratios.
5. Chemical reactions occur when
atoms separate from each other, join with others,
but the atoms themselves never change.
J.J. Thompson (1897):
Discovered the electron.
Electrons have negative charge.
Pictured atoms as a spheres with
tiny, negative charges embedded
throughout.
Came up with the “plum pudding”
model of the atom.
Millikan (~1900) his oil drop experiment discovered mass/charge
of electron.
Ernest Ruthorford (1911): Discovered the nucleus of the atom
in his famous “Gold Foil Experiment”.
Nucleus is small, dense, positively-charged center of the atom.
Electrons move around the nucleus.
Niels Bohr (1913):
Planetary model of atoms.
Electrons move around nucleus
in fixed orbits,
based on energy levels,
like planets around the sun.
While not entirely accurate, his model
is still often used today to provide visualization.
Chadwick (1932):
discovered neutron
Subatomic particles
Particle
Symbol
p+
Electron e–
Neutron no
Proton
Charge
Mass in grams Mass in amu
+1
1.67x10-24
1
-1
9.11x10-28
1/1840
0
1.67x10-24
1
Protons and neutrons are located in the nucleus, are the same size,
and contribute to mass.
Electrons are located outside the nucleus, and are so small they don’t
contribute to mass.
Electron movement is the basis of chemistry!
You MUST Remember the charge and location of EACH subatomic particle!
Trivias
500,000,000,000,000,000,000,000,000,000,000 electrons equals 1pound
2,500,000,000,000 protons side by side = 1 inch
Ex1)
a) If an oxygen atom consists of a nucleus with eight protons and eight
neutrons, what is the charge of that nucleus?
b) If there are eight electrons surrounding that nucleus,
what is the overall charge of this oxygen atom?
c) What is the total mass of this atom in amus?
Ch4 HW#1
Ch4 HW#1 1 – 4
1. Explain how Democritus came up with his theory every made of atoms:
2. Which statement would Dalton Agree with:
a) Atoms are the smallest particles of matter.
b) Mass of an iron atom is different from mass of a copper atom.
c) Every atom of silver is Identical to every other atom of silver.
d) A compound is composed of atoms of two or more different
elements.
3. What did Rutherford’s gold foil experiment unexpectedly find?
4. a) If a fluorine atom consists of a nucleus with nine protons and
nine neutrons, what is the charge of that nucleus?
b) If there are nine electrons surrounding that nucleus,
what is the overall charge of this fluorine atom?
c) What is the total mass of this atom in amus?
d) In nature, fluorine is always found with 10 electrons rather than nine
surrounding its nucleus. What is the overall charge of this atom?
Ch 4.2 - The Periodic Table
6
C
Carbon
12.011
Atomic #:
Mass #:
2
4
Ch 4.2 - The Periodic Table
Atomic #
Mass #
6
C
Carbon
12.011
2
4
Electron
Locations
_p
_n
Atomic #: # of protons
- the periodic table is arranged in increasing atomic #.
- since all atoms are electrically neutral # protons = #of electrons
Mass #: total mass of atom mass = protons and neutrons
- do not count electrons → too small!
Getting Subatomic Particles from the Periodic Table
Mass # (prots & nuets)
Ex1)
16
O
8
protons =
Atomic # (prots)
electrons =
Neutrons = mass # – atomic # =
neutrons =
Ex2)
108
Ag
47
____Protons, ____ electrons, ____ Neutrons
Ex3) Sometimes written is this form :
Carbon – 12
____Protons, ____ electrons, ____ Neutrons
Uranium – 238 ____Protons, ____ electrons, ____ Neutrons
Isotope #
HW#5) (copy to separate paper!)
Element
Potassium
Symbol
Atomic # # of protons
5
16
Y
HW#6)
Atomic #
Mass #
# Protons
9
#Electrons Symbol
10
14
47
55
Ch4 HW#2 5 - 8
# Neutrons
15
22
25
Ch4 HW#2 5 – 8
5)
Element
Potassium
Symbol
Atomic # # of protons
5
16
Y
6) Atomic #
Mass #
# Protons
9
# Neutrons
#Electrons Symbol
10
14
47
55
15
22
25
7. An atom is identified as platinum- 195.
a. What is the number 195 called?
b. What is the symbol with #’s?
8. Determine the number of neutrons in each atom.
a. carbon-13
b. nitrogen-15
c. radium-226
Ch4.3 Atomic Mass
(Hand out periodic table)
1 Flourine atom has a mass of: 0.000 000 000 000 000 000 000 03155g
What is that!
How about in scientific notation:
Ch4.3 Atomic Mass
1 Flourine atom has a mass of: 0.000 000 000 000 000 000 000 03155g
What is that!
How about in scientific notation:
3.155x10–23 g
Looks better,
but still not practical
Ch4.3 Atomic Mass
1 Flourine atom has a mass of: 0.000 000 000 000 000 000 000 03155g
What is that!
How about in scientific notation:
3.155x10–23 g
Looks better,
but still not practical
It was decided a smaller mass measurement is needed.
mass of 1 proton = 1 atomic mass unit
- since protons and neutrons are extremely close in mass,
it was decided that 1 amu would be based on Carbon-12
With 6 protons and 6 neutrons, then ÷ by 12 nucleons = 1 amu
Ch4 HW#3 9.
Fill in the missing information, then draw Bohr models of the atoms,
based on the electron locations listed on your periodic table.
Element
Symbol Mass Atomic Protons Neutrons
#
#
Aluminum Al
27
Carbon
12
13
3
6
Chlorine
17
18
Chromium
24
28
Cobalt
Copper
32
64
Gold
119
Helium
2
Hydrogen
Iron
1
Period Group
(Row) (Column)
0
30
13
Ch4 HW#3 9.
Fill in the missing information, then draw Bohr models of the atoms,
based on the electron locations listed on your periodic table.
From P.T.:
2
Symbol
10
Al
3
13p
13
C
Cl
Cr
Co
Cu
Au
He
H
Fe
Al
Aluminum
27.0
14n
Ch4 HW#3 9.
Fill in the missing information, then draw Bohr models of the atoms,
based on the electron locations listed on your periodic table.
Symbol
Al
C
Cl
Cr
Co
Cu
Au
He
H
Fe
Ch4.4 Isotopes and Average Atomic Mass
Isotopes of the SAME ELEMENT obviously have the same # of protons,
but differ in # of neutrons
Ex1) Write the chemical symbol and find # of neutrons for:
Carbon-12 and Carbon-13
Average Atomic Mass
- each element can have many naturally occurring isotopes.
The periodic table lists the mass of each element
as an average based on the relative abundance of the isotopes.
H – 1.0079 C – 12.011 -
Cl – 35.435 -
H – 1.0079 ( Over 99% of all hydrogen's are H – 1)
( A few are H – 2, or H – 3)
C – 12.011 ( Almost all are C – 12)
Cl – 35.435 - only 2 isotopes → Cl – 35 & Cl – 37
75% in nature are Cl – 35
25% are Cl – 37
So these are weighted averages
Ex2) In nature, magnesium has three common isotopes.
The 3 isotopes and their relative abundance are as follows:
79% is Mg-24
10% is Mg-25
11% is Mg-26
All of these are stable.
Calculate the average atomic mass of Mg.
Ex3) In nature, strontium has four stable isotopes.
The 4 isotopes and their relative abundance are as follows:
Sr-84
0.5%
Sr-86
9.9%
Sr- 87
7.0%
Sr-88 82.6%
Calculate the average atomic mass of Sr.
Ch4 HW#4 10-15
Ch4 HW#4 10-15
10) How are isotopes of the same element alike? How are they different?
11) Three isotopes of oxygen are Oxygen – 16, Oxygen – 17, and Oxygen – 18,
write the chemical symbol.
12) Determine # of prots, elects, Neuts for the 5 isotopes of zinc
p+
Zn-64
Zn-66
Zn-67
Zn-68
Zn-70
e–
no
13) There are 3 isotopes of silicon with mass #’s 28, 29, 30.
The atomic mass of silicon is 28.086 amu. Which is most abundant?
14) The element copper has 2 naturally occurring isotopes:
63
29
Cu, 6529 Cu.
The relative abundances are: Cu–63: 69.2% and Cu–65: 30.8%
Calculate the average atomic mass.
13) There are 3 isotopes of silicon with mass #’s 28, 29, 30.
The atomic mass of silicon is 28.086 amu. Which is most abundant?
14) The element copper has 2 naturally occurring isotopes:
63
29
Cu, 6529 Cu.
The relative abundances are: Cu–63: 69.2% and Cu–65: 30.8%
Calculate the average atomic mass.
Cu – 63: 0.692 x 63 =
Cu – 65: 0.308 x 65 =
15) The element mercury has 6 naturally occurring isotopes.
The relative abundances are:
Hg–198: 10%, Hg–199: 17%, Hg–200: 23%,
Hg–201: 13%, Hg–202: 30%, Hg–204: 7%,
Calculate the average atomic mass.
Chapter 25.1 Nuclear Chemistry
Ex: Carbon – 14
6P
8N
What does the nucleus look like?
Ex: Carbon – 14
What does the nucleus look like?
It is more realistic to picture a nucleus
as a swarm of bees,
rather than a bunch of grapes.
Ex: Carbon – 14
What does the nucleus look like?
It is more realistic to picture a nucleus
as a swarm of bees,
rather than a bunch of grapes.
Some isotopes of some elements contain
and unstable ratio of protons to neutrons.
These Radioisotopes are radioactive
because they have unstable nuclei.
They undergo radioactive decay
The decay may be just a release of energy
or it may be a complete break apart.
Types of Radiation
1. Alpha radiation – a helium nucleus is emitted from a radioactive source
Ex) 23892U
→ 22490Th
Uranium – 238
Thorium – 234
+
4
2
He
Alpha particle
4 He
2
238 U
92
Alpha radiation, aka: α emission, is:
Low Energy
Low Penetrating Power
224 Th
90
2. Beta radiation – an unstable nucleus decays, releases a beta particle
- a neutron decomposes into a proton and an electron
Ex1)
1 n
0
→
Neutron
Ex2)
14 C
6
1 H
1
+
Proton
→
Radioactive
Carbon – 14
↑
p=6
n=8
14 N
7
Electron
(beta particle)
+
Stable
Nitrogen – 14
↑
p=7
n=7
Beta radiation, aka: β emission, is:
Mid Energy
Mid Penetrating Power
0 e
-1
0 e
-1
Beta
Particle
3. Gamma radiation – an unstable nucleus decays, releasing high energy
electromagnetic radiation.
Ex3) 23090Th
Thorium – 230
→
226 Ra
88
Radon – 226
+
4 He
2
Alpha
Particle
Gamma radiation, aka: γ emission, is:
High Energy
High Penetrating Power
+
γ
Gamma
Radiation
Ex4) Name the emitted particle and find the new nuclei created:
a.
218 Fr→
87
214 At
85
b.
241 Am
95
→
c. 23592U
→
90 Sr
38
4 He
2
+
____
+
____
+ _____ +
d. ____ + 23994Pu → 14458Ce + 9038Sr
What happened to this poor plutonium?
Ch25 HW#1
1 N
0
+ 4 0-1e
+ 6 10n + 2 0-1e
Ch25 HW#1
1) What part of the atom changes during radioactive decay?
2) Tell how alpha, beta, and gamma radiation are distinguished based on:
a) atomic mass
b) charge
c) penetrating power
α:
β:
γ:
3) The disintegration of the radioisotope radium-226 produces an isotope
of the element radon and alpha radiation write eqn:
1) What part of the atom changes during radioactive decay?
2) Tell how alpha, beta, and gamma radiation are distinguished based on:
a) atomic mass
b) charge
c) penetrating power
α:
β:
γ:
4
2He
0 e
-1
no mass, all energy
+2
–1
no charge, all energy
low
mid
high
3) The disintegration of the radioisotope radium-226 produces an isotope
of the element radon and alpha radiation write eqn:
4) Write nuclear eqns:
a) 30 15
P to 30 14 Si
b) 13 6
12
C to
6
C
5) Complete:
a) 3015P → 3016S + 0-1e
b) 148O →147N + 0-1e
c) 23892U → 23490Th + ___
d) 14156Ba → ___ + 0-1e
6) Beta decay the following:
a) 9038Sr →
b) 146C →
c) 13755Cs →
d) 23993Np →
Ch25.2 Half Life
aka:
(t ½)
- The time required for ½ the atoms of a radioisotope to decay.
Ex 1) Nitrogen – 13 emits beta radiation (in the form of a positron)
and decays to Carbon – 13 with a half life of 10 min.
With a starting mass of 2.00g of N – 13,
a) how long is 4 half lives?
b) how many grams of N – 13 still exist after 3 half lives?
Carbon Dating
- developed in 1940’s
- 146C
→ 147N + 0-1e
- t1/2 = 5730 years
- fairly accurately dates non-living things 200-50,000 yrs
How do we date the dinos?
Use a radioisotope with a longer ½ life
- uranium – 238 → t1/2 = 4.5 x109 yrs
(4.5 billion yrs!)
- use this to age certain rocks, all the back to beginning of
our solar system 4.6 billion years.
Ex 2) What is the ½ life of this radioisotope ?
If you had 20.0 g of it, how much
remains after 10 years?
10075amt
%
5025-
5
10
15
t (years)
20
25
Ex 2) What is the ½ life of this radioisotope ? 5 yrs
If you had 20.0 g of it, how much
remains after 10 years?
100(2 half-lives) 5g
75amt
%
5025-
5
10
15
t (years)
20
25
Nuclear Fission and Fusion
Fission-the splitting of a nucleus into smaller fragments caused
by bombarding it with neutrons
-releases enormous amounts of energy
( 1 kg of U-235 = 20,000 tons of TNT)
→
235 U
92
236 U
92
91 Kr
36
Step 1: 10n
+ 23592U →
236 U
92
Step 2 23692U
→ 9136Kr + ___ + 3 10n
Fusion – 2 nuclei combine to produce a nucleus of heavier mass
In the sun:
4
1 H
1
+ 2
0 e
-1
→
4 He
2
+ energy
Fusion releases more energy than fission
but requires high temps → 40,000,000 0C
Cold fusion occurs at easily achievable temps:
2 H
1
Ch25 HW#2
+ ___ →
4 He
2
+
1 n
0
+ energy
Ch25 HW#2 7 – 14
7) A sample of thorium – 234 has a half-life of 25 days. Will all the thorium
undergo radioactive decay in 50 days?
8. Manganese-56 is a beta emitter with a half-life of 2.6h.
What is the mass of manganese-56 in a 1-mg sample of the isotope after 10.4 h?
10.4 ÷ 2.6 = 4 half lives
9) Explain nuclear chain reaction.
10) How is the chain reaction controlled in a reactor?
11) Name a natural nuclear fusion reactor
12) What are advantages of producing electricity in a fusion reactor?
13) Write: a) a radon emits an alpha particle to form polonium – 218
b) Radium – 230 is produced when thorium 234 emits alpha
c) When polonium – 210 emits alpha particle, product is Pb – 206
14. Graph the decay of Thorium 234
100
80
%
60
Remaining 40
20
20 40 60 80 100
days
a) What percent after 60 days?
b) How many grams of a 250g sample remain
after 40 days?
c) How many days would pass while 44g decayed
to 11g?
d) What is half-life?
Ch4,25 Review
1. List the # of protons, neutrons, electrons for each atom:
a. 2713 Al
b. 4420 Ca
c. 31H
p:
n:
e:
2. What is the average mass of Lead?
204 Pb @ 1.37%
82
206 Pb @ 26.26%
82
207 Pb @ 20.82 %
82
208 Pb @ 51.55%
82
Element
# of
Protons
Mass
Number
# of
Atomic #
Electrons
Si
Number
Neutrons
15
1
2
50
88
24
38
Symbol
4.
Charge
Mass
Penetrating Power
alpha particle
beta particle
gamma ray
5. Complete the following nuclear equations:
a. 2713 Al + 42 He 3014 Si
b. 21483 Bi
c. 2714
+ ______
42 He + ______
Si 0-1 e + ______
6. A patient is administered 20 milligrams of iodime-131, how much of the isotope
will remain in the body after 40 days if the half-life of I-131 is 8 days?
1
2
3
4
5
7. Know the science guys, Dalton’s atomic theory, and read your notes.
Element
Symbol Mass Atomic Protons Neutrons
#
#
Krypton
Lead
47
208
Mercury
125
121
Nitrogen
14
7
Potassium
39
20
Silver
61
Sodium
12
Sulfur
32
16
Uranium
146
Zinc
35
Period Group
(Row) (Column)
Electron Shells Worksheet
1.
1
1 Electron
1
H
1p
0n
Hydrogen
1.0074
2.
2
1
3
Li
Lithium
6.941
3p
4n
3.
2
3
_
__
_p
_n
Boron
______
4.
_
_
_
__
Nitrogen
______
_p
_n
2
8
8
1
9.
_
K
_p
_n
Potassium
______
10.
30
Zn
Zinc
65
30p
35n
15) List the # of protons, neutrons, electrons
a) 2713Al
p+
no
e-
b) 4420Ca
c) 31H
d) 188O
e) 7834Se