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The center of the atom
Nucleus
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Ernest Rutherford introduced the nuclear model, which described the atom as containing a small, dense, (positive or negative) charged center surrounded by a (positive or negative) cloud of electrons.
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Bohr's model was a miniature solar system in which the electrons revolved about the nucleus in prescribed orbits or _____.
energy levels
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Bohr Atom represents the best way to picture the atom, although the details of atomic structure are more accurately described by a newer model called
quantum chromodynamics (QCD)
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"Atom smashers", the structure of the atomic nucleus is slowly being mapped and identified.
particle accelerators
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The three primary constituents of an atom also known as fundamental particles:
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The 3 fundamental particles of an atom are:
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very small particles that carry one unit of negative electric charge.
electons
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An atomic particle is extremely small, its mass is expressed in
Atomic Mass Unit (amu)
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One atomic mass unit is equal to ___ the mass of a carbon-12 atom.
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When precision is not necessary, a system of whole numbers used is called
mass numbers
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The atomic mass number of an electron is
zero
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The nucleus contains particles called
nucleons
-
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Protons and neutrons both have nearly how times the mass of an electron?
2000
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Essentially empty space.
Atom
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The number of protons determines the
chemical element
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Atoms that have the same number of protons but differ in the number of neutrons are
isotopes
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Electrons can exist only in certain ___, which represent different electron binding energies or ____ ____.
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For identification purposes, electron orbital shells are given the codes (name 1st four) to represent the relative binding energies of electrons from closest to the nucleus to farthest from the nucleus
K, L, M, N
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The closer an electron is to the nucleus, what energy is greater?
binding energy
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What are electrically neutral in their normal state?
Atom
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The removal or addition of an orbital electron from an atom
Ionization
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The mass number of electrons that can exist in each shell (decrease or increase) with the distance of the shell from the nucleus.
increases
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The total number of electrons in the orbital shells is exactly equal to the number of ____ in the _____
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An atom has an extra electron or has had an electron removed is
ionized
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An ionized atom is not electrically neutral but carries a charge equal in magnitude to the difference between the numbers of ____ and ____
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How the maximum electrons per shell is calculated
2n2
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What is the maximum number of electrons that can exist in the O shell (shell number 5)
- n = 5
- 2n2 = 2(5)2
- = 2 (25)
- = 50 electrons
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What is the shell number for each symbol:
K, L, M, N, O, P, Q
- K = shell 1
- L = shell 2
- M = shell 3
- N = shell 4
- O = shell 5
- P = shell 6
- Q = shell 7
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Calculate the number of electrons that can occupy each electron shell for the following: 2n2
K, L, M, N
- K = 2(12)
- = 2(1) = 2 electrons
- L = 2(22)
- = 2(4) = 8 electrons
- M = 2(32)
- =2(9) = 18 electrons
- N = 2(42)
- = 2(16) = 32 electrons
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No outer shell can contain more than ____ electrons
8
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What does Physicists call the shell number n
principal quantum number
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"center-seeking" force, which results from a basic law of electricity that states that opposite charges attract one another and like charges repel.
centripetal force
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The force that keeps an electron in orbit is
centripetal force
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The strength of attachment of an electron to the nucleus is called
electron binding energy
-
Note:
K-shell electrons have higher binding energies than L-shell electrons, L-shell electrons are more tightly bound to the nucleus than M-shell electrons, and so forth.
-
The atomic mass number and the precise mass of an atom are (equal or not equal)
equal
-
A whole number that is equal to the number of nucleons in the atom
atomic mass number
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The characteristic mass of an element is determined by the relative abundance of isotopes and their perspective atomic masses
elemental mass
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Atoms that have the same atomic number but different atomic mass numbers are
isotopes
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Atomic nuclei that have the same atomic mass number but different atomic numbers are
isobars
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The atoms that have different numbers of protons and different numbers of neutrons but the same total number of nucleons
Isobars
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Atoms that have the same number of neutrons but different numbers of protons are
isotones
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Atoms with different atomic numbers and different mass numbers but a constant value for the quantity A-Z.
Isotones
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Atoms with the same number of neutrons in the nucleus
Isotones
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Have the same atomic number and the same atomic mass number.
Isomer
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Atoms of various elements may combine to form structures called
Molecules
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Any quantity of one type of molecule
Chemical compound
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Similarly, hydrogen, oxygen, carbon, and nitrogen compose more than ____% of the human body.
95%
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At approximately what % water molecules make up of the human body?
80%
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Oxygen and hydrogen combine into water through what type of bonds.
Covalent bonds
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Sodium and chlorine combine into salt through what type of bond?
Ionic bonds
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A measurable quantity of sodium bicarbonate constitutes a chemical compound commonly called
Baking soda
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Some atoms exist in an abnormally excited state characterized by an unstable nucleus. To reach stability, the nucleus spontaneously emits particles and energy and transform itself into another atom. This process is called _____ _____ or _____ _____
- Radioactive disintegration
- Radioactive decay
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Any nucleus that emits radiation; Only nuclei that undergo radioactive decay are
Radionuclides
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Process by which the nucleus spontaneously emits particles and energy and transforms itself into another atom to reach stability.
Radioactive disintegration
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Naturally occurring process whereby an unstable atomic nucleus relieves its instability through the emission of one or more energetic particles
Radioactive decay
-
Any nuclear arrangement; General term that refers to all known isotopes, both stable and unstable, of chemical chemical elements
Nuclide
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The emission of particles and energy in order to become stable
Radioactivity
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In addition to stable isotopes, many elements have ____; these may be artificially produced in machines such as particle accelerators or nuclear reactors.
radioisotopes
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Two ways radioisotopes can decay to stability; Radioactive decay by positron emission is important for some nuclear medicine imaging.
- beta emission
- alpha emission
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An electron created in the nucleus is ejected from the nucleus with considerable kinetic energy and escapes from the atom
beta emission
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Much more violent process; Alpha particle consist of two protons and two neutrons bound together; Its atomic mass number is 4
Alpha emission
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What results in emission of alpha particles, beta particles, and usually gamma rays?
Radioactive decay
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The rate of radioactive decay and the quantity of material present at any given time are described mathematically by a formula know as the
Radioactive decay law
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From the radioactive decay law, what is this formula (T 1/2)
half-life
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What radioisotopes vary from less than a second to many years. Each radioisotope has a unique, characteristic half-life?
Half-lives
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Used daily in nuclear medicine and has an exact parallel in x-ray terminology
Half-value layer
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3.3 half lives =
1 tenth life
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How many half-lives are required before a quantity of radioactive material has decayed to less than 1% of its original value?
- Half-life number Radioactivity remaining
- 1 50% (half of 100%)
- 2 25% (half of 50)
- 3 12.5% (half of 25)
- 4 6.25% (half of 12.5)
- 5 3.12% (half of 6.25)
- 6 1.56% (half of 3.12)
- 7 0.78% (half of 1.56)
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Two main types of particulate radiation; Both are associated with radioactive decay.
- alpha particles
- beta particles
-
Equivalent to a helium nucleus, contains 2 protons and 2 neurtons, its mass is approx 4 amu, and it carries 2 units of positive electric charge
Alpha particle
-
Note:
Because of the amount of ionization, the energy of an alpha particle is quickly lost. It has a very short range in matter. Whereas in air, alpha particles can travel approx 5 cm; in soft tissue, the range may be less than 100 um
-
An electron emitted from the nucleus of a radioactive atom; they are light particles with an atomic mass number of 0 and carry one unit of negative or positive charge.
beta particle
-
All ionizing radiation can be conveniently classified into two categories:
- particulate radiation
- electromagnetic radiation
-
The types of radiation used in diagnostic ultrasonography and in magnetic resonance imaging are
nonionizing radiation
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Depending on its energy, a beta particle may traverse ___ to ___ cm of air and approximately __ to __ cm of soft tissue.
- 10 to 100 cm of air
- 1 to 2 cm of soft tissue
-
Type of rays that are forms of electromagnetic ionizing radiation
-
X-rays and gamma rays are often called
Photons
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What have no mass and no charge & they travel at the speed of light? (c = 3 x 108 m/s) and are considered energy disturbances in space.
Photons
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What rays exist at the speed of light or not at all?
-
Characteristics of Various Nuclear Arrangements (Table 2-4) page 36
-
A method of association to help with the "iso" definitions is:
- isotope, same proton
- isobar, same A (Atomic Mass Number)
- isotone, same neutron
- isomer, metastable (all are the same)
-
As a miniature solar system, what set the stage for the modern interpretation of the structure of matter?
Bohr atom
-
What is the smallest part of an element? and what is the smallest part of a compound?
-
Negatively charged particles that orbit the nucleus in configurations or shells held in place by electorstatic forces.
Electrons
-
Reaction that occur when outermost orbital electrons are shared or given up to other atoms.
Chemical reaction
-
Positively charged, and neutrons have no charge
Protons
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What are grouped in a periodic table in order of increasing complexity; The groups on the table indicate the number of electrons in the outermost shell.
Elements
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Some atoms, which contain too many or too few neutrons in the nucleus, can disinergrate, this is called
Radioactivity
-
What is a radioisotope is the time required for the quantity of radioactivity to be reduced to one-half its origianl value
half-life
-
Rays that are produced in the electron shells
x-rays
-
Rays that are emitted from the nucleus of a radioiosotope
gamma rays
-
This particle originate in the nucleus of radioactive atoms
Beta particles
-
The electric charge on the atom is ____
Zero
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What is the smallest particle that has all the properties of an element?
Atom
-
What is the center of the atom?
Nucleus
-
particle accelerators =
atom smashers
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Only the 3 primary constituents of atom, the electron, the proton,and the nuetron, are considered here. They are the ______ ______.
fundamental particles
-
note:
The fundamental particles of an atom are the electron, the proton, and the neutron.
-
_________ are very small particles that carry one unit of negative electric charge
Electrons
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Because an atomic particle is extremely small, its mass is expressed in _____ _____ _____ for convienence.
Atomic mass units (AMU)
-
When precision is not necessary, a system of whole numbers called atomic mass _______ is used.
numbers
-
The atomic mass number of an electron is
zero
-
The nucleus contains particles called ______, of which there are 2 types: protons & neutrons. Both have nearly 2000 times the mass of the electron.
nucleons
-
note:
The atom is essentially empty space
-
The number of protons determines the _______ ______. Atoms that have the same number of protons but differ in the number of neutrons are isotopes; they behave the same way during chemical reactions.
chemical elements
-
Electrons can exist only in certian shells, which represent different _______ _______ _______ or energy levels.
electron binding energies
-
In their normal state atoms are electrically _______, the electric charge on the atoom is zero.
neutral
-
If an atom has an extra electron or has had an electron removed, it is said to be ________.
ionized
-
note
Ionization is the removal or addition of an orbital electron from an atom.
-
The maximum number of _______ that can exist in each shell increases with the distance of the shell from from the nucleus.
electrons
-
Maximum electrons per shell can be calculated by:
2n squared
-
NO outer shell can contain more than ____ electrons
8
-
_________ force; is a force theat keeps an electron in orbit
Centipetal
-
the force that keeps an electron in orbit is __________
__________.
Centripetal force
-
The _____ _____ causes an electron to travel straight and leave the atom.
- Centrifugal force.
- The centrifugal force makes sure that the electrons maintain their distance from the nucleus while traveling in a circular path.
-
The strength of attachment of an electron to the nucleus is called the _____ _____ _____.
- electron binding energy
- The closer an electron is to th nucleus, the more tightly it is bound. K shell elcetrons have higher binding energies than L shell electrons. L more than M and so forth
-
Note
The Atomic Mass number and the precise mass of an atom are not equal.
-
Any nuclear arrangement is called a _____?
nuclide
-
Note:
Radioactivity is the emission of particles and energy in order to become stable
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