CP NT Ch. 4&25
I. Atomic Theory and Structure of the Atom
a. Democritus—all matter consists of very small, indivisible particles, which he named ________
i. Atom—smallest particle of an element that retains all properties of the element
b. Dalton—proposed an “atomic theory” composed of four hypotheses detailing spherical
solid atoms
i. Elements are composed of extremely small particles called atoms
ii. Atoms of the same element are _____________________; each element is different from
the atoms of all other elements
iii. Compounds are composed of atoms of more than one element. In any compound,
the ratio of the numbers of atoms present are in small whole numbers
iv. A chemical reaction involves only the separation, combination, or rearrangement of
atoms; it does not result in their creation or destruction
c. The electron—_______________________ charged subatomic particle
i. symbol: e−
d. J.J. Thomson
i. Model of the atom: p______________ p_________________ model; an atom is thought of as a
uniform, positive sphere of matter in which electrons are evenly distributed through
out
ii. Used the cathode ray tube to find the charge to mass ratio of an _______________________
e. Millikan
i. Oil drop experiment
ii. Mass of an electron: 9.10×10−28 g
f. Rutherford
i. Model of the atom: nuclear model; small dense core with electrons around the
outside making up almost all of the volume; most of the atom is _________________space
ii. Gold foil experiment—shot a beam of alpha
particles at a gold foil. With the current model
of the atom (Plum Pudding) he expected them
to go straight through and hit the detector on
the other side, INSTEAD he saw some go
through, and others come straight back. This
lead him to change the model of the atom
iii. Nucleus—dense central core of the atom;
contains all the _______________________
iv. Proton—positively charged subatomic particle located in the ______________________
1. Mass: 1.67262×10−24 g
2. Symbol: p+
g. Bohr
i. Planetary model of the atom: expanded on the nuclear atom; put electrons in
concentric _______________________orbits around the nucleus
h. Schrödinger
i. Quantum Mechanical model of the atom: viewed electrons as continuous _____________
i. Chadwick
i. Neutron—electrically _______________________subatomic particle
1. Symbol: n0
2. Mass: 1.675×10−24 g
1
Particle
Symbol
Location
Relative
Charge
Relative
mass
Actual mass (g)
-28
Electron
9.11 x 10
Proton
1.673 x 10
Neutron
1.675 x 10
-24
-24
II. How Atoms Differ
a. Properties of subatomic particles
b. Atomic Number—number of _______________________in the nucleus
c. Mass number—__________________number of protons and neutrons in the nucleus of an atom
d. Isotopes—atoms that have the same atomic number (# of protons) but different mass
Mass number
numbers due to different number of neutrons
238
235
𝐴
i. Example 92 U (uranium—235) and 92 U (uranium—238)
X
𝑍
atomic number
e. Average atomic mass—weighted _______________________of the isotopes of that element
i. Formula:
% 𝑎𝑏𝑢𝑛𝑑𝑎𝑛𝑐𝑒 𝑜𝑓
𝑚𝑎𝑠𝑠 𝑜𝑓
% 𝑎𝑏𝑢𝑛𝑑𝑎𝑛𝑐𝑒 𝑜𝑓
𝑚𝑎𝑠𝑠 𝑜𝑓
𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑎𝑡𝑜𝑚𝑖𝑐 𝑚𝑎𝑠𝑠 = (
×
)+ (
×
)
𝑖𝑠𝑜𝑡𝑜𝑝𝑒 1
𝑖𝑠𝑜𝑡𝑜𝑝𝑒 1
𝑖𝑠𝑜𝑡𝑜𝑝𝑒 2
𝑖𝑠𝑜𝑡𝑜𝑝𝑒 2
ii. Example 1: Silver has two naturally occurring isotopes. Ag-107 has an abundance of
51.82% and mass of 106.9 amu. Ag-109 has a relative abundance of 48.18% and a
mass of 108.9 amu. Calculate the atomic mass of silver.
iii. Rubidium is a soft, silvery-white metal that has two common isotopes, 85
37Rb and
87
85
87
37Rb. If the abundance of Rb is 72.2% and the abundance of Rb is 27.8%, what is
the average atomic mass of rubidium?
III. Nuclear Chemistry
a. Chemical vs. nuclear reactions
i. Chemical reactions involve an atom’s _______________________where nuclear reactions
involve changing an atoms nucleus
ii. Nuclear rxns release about a million times ________________energy than chemical rxns
2
b. Electrostatic force—when like charges repel and opposite charges attract
c. Strong Nuclear Force—attractive force that acts between all nuclear particles that are
extremely close together; keeps the _______________________together
d. Radiation—the emission (and transmission) of energy through space in the form of waves
e. Radioactivity—spontaneous emission of particles and/or radiation
i. Alpha—particle that contains two protons and two neutrons (He nucleus)
4
4
1. Symbol: 𝐻𝑒 or 𝛼
2
2
2. Charge: +2
3. _______________________penetration form of radiation (blocked by paper)
ii. Beta—fast moving electrons
0
0
1. Symbol:
𝑒 or
𝛽
−1
−1
2. Charge: −1
3. medium penetration (blocked by metal foil or wood)
iii. Gama—high energy radiation that possesses no mass
0
1. Symbol: 𝛾
0
2. Charge: none
3. _______________________penetrating and damaging type of radiation (not
completely blocked by lead or concrete)
f. Radioactive—any element that spontaneously emits radiation (shows signs of
radioactivity)
i. Transmutation—changing of an atom’s nucleus such that a _______ element is formed
1. Alpha and beta radiation are transmutations, while neutron and gamma are
not
2. Can be induced (caused)
a. Before 1919 the only way to change the nucleus, or cause
transmutation, was to wait for _____________________, but in 1919
Rutherford was the first to induce transmutation which proved that
nuclear reactions can be produced artificially.
b. Can occur by _______________________an atom with alpha particles,
protons, or neutrons
3. Transuranium elements—all undergo transmutation and were produced
through induced transmutation (elements beyond uranium)
ii. Radioactive nuclei are found _______________________the band of stability and undergo
decay to gain stability
g. Radioactive decay—unstable nuclei losing energy by emitting radiation in a spontaneous
process
i. Band of stability—stability of the nucleus depends on the neutron to proton _________
h. Radioisotope—isotopes of atoms with unstable nuclei and go through radioactive decay to
obtain a more stable nuclei
i. Small nuclei—up to 20 protons, usually stable
1. Exception example: Carbon-12 (6 p+ and 8 n0) vs Carbon-14 (6 p+ and 8 n0)
ii. Large nuclei—tend to be radioactive, based on ratio of protons to neutrons; ALL
nuclei with 83 protons or more are _______________________
i. Electron Capture—occurs when a nucleus of an atoms draws in an electron; also known as
beta capture
81
81
0
i. Example: 𝑅𝑏 +
𝑒 →
𝐾𝑟
37
36
−1
3
j.
Nuclear Equations
i. In a balanced nuclear equation, mass numbers and atomic numbers are ______________
230
226
4
ii. Example:
𝑇ℎ →
𝑅𝑎 + 𝐻𝑒
90
88
2
iii. Practice
97
0
47
0
1.
𝑍𝑟 →
𝑒+?
4.
𝐶𝑎 →
𝑒+?
40
−1
20
−1
218
4
244
4
2.
𝑃𝑜 → 𝐻𝑒 + ?
5.
𝐶𝑚 → 𝐻𝑒 + ?
84
96
2
2
222
4
3. ? →
𝑅𝑛 + 𝐻𝑒
86
2
k. Half-Life—________ required for one-half of a radioisotope’s nuclei to decay into its products
i. After each half-life, half of the existing radioactive atoms have decayed into atoms of
a new element
1
total time
ii. Equation: 𝑇 = (𝑖𝑛𝑖𝑡𝑖𝑎𝑙 𝑎𝑚𝑜𝑢𝑛𝑡)(2)𝑛 n=number of half-lives; n = time of one half−life
iii. Practice
1. Scientists start with 50.0 g sample of a radioisotope. How much is left after
four half-lives?
2. Iron-59 is used in medicine to diagnose blood circulation disorders. The halflife of iron 59 is 44.5 days. How much of a 2.000 mg sample will remain after
133.5 days?
iv. Carbon-14 dating
1. Process of determining the age of artifacts that were once part of a living
organism by measuring the amount of 146𝐶 remaining in that artifact
2. Radioactive and undergoes beta decay
3. Half-life of 5730 years
4. Dates carbon-bearing materials up to 62,000 years
Using the graph, about
how much strontium-90
remains after 58 years?
4
IV. Nuclear Fission and Fusion
a. Fission—the splitting of the nucleus into _________________________ (division)
i. Chain reaction—nucleus captures a neutron and splits into fragments and produces
three neutrons, then the products start a _____________ reaction (domino effect)
1. Critical mass—the _________________________ mass required to support a selfsustaining chain reaction
b. Fusion—_________________________ atomic nuclei to produce a nucleus of greater ________________
i. Releases more energy than fission
ii. Example: the sun (all stars)
c. Nuclear binding energy—the energy required to break a nucleus into its individual protons
and neutrons
i. Energy released in a nuclear reaction is much greater than in a chemical
reaction
d. Mass Defect—when breaking apart a nucleus, there is a change in mass; some of the mass is
converted to energy; E=mc2
e. Nuclear Reactors—to keep the chain reaction going without letting it get out of ______________
f. Nuclear Bombs
i. Atomic Bomb
1. Uses fission
2. Enriched uranium-235 or plutonium
3. Example: Nagasaki and Hiroshima
ii. Hydrogen Bomb
1. Uses fusion
2. 1000 times more powerful
3. uses deuterium and tritium
Well-known example of fission: Uranium-235 is
struck by a neutron and forms Ba-141, Kr-92,
and additional neutrons.
5
A well-known example of fusion: the sun has
deuterium and tritium coming together to make
a helium atom