atomictheory_web_f12_000.pdf

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Principles of Imaging Science I (RAD119)

Physics Fundamentals &

Atomic Structure

Goals Understand the structure of matter and the

fundamentals of electromagnetic radiation.

Understand the concept of x-ray production, how x-rays interact with matter, the quantity and

quality of the x-ray beam, and demonstration of

anatomic structures in the radiographic image (radiograph)

An Art and a Science

Radiography as art

Scientific method

Natural science

o Physical science: non-living matter

Physics

o Biological science: living matter

Anatomy and Physiology

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Matter and Energy

Physics studies relationships between matter and energy

Matter o Mass and occupies space

Energy is force used to do work

Matter Matter

Anything that occupies space, has shape or form, and has mass

States of matter: Solid, liquid, gas

Mass Amount or quantity of matter in an object.

Does not change with a change in the form

Does not change with gravitational force

Air has mass, but much less than a rock that has the same volume because the particles of matter in air are

more widely spaced.

Fundamental Unit - Atom Composed of smaller units protons,

neutrons, and electrons

Atomic Theory

Basic building blocks of matter

Atom is unique and characteristic of a certain type of matter

oHydrogen atom is different from an atom

of Barium or Calcium

Atoms cannot be seen o Scientists theorized about its structure and function based

on experimentation

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Atomic Structure

Nucleus

Small, dense center

Contains nucleons protons and

neutrons

Electrons

Orbit nucleus

Bohr Atom Basic structure of atoms is comparable to

our solar system

An atom is mostly empty space the space between the electrons and the nucleus is like the space between the earth and sun

Atom is comprised of a small, dense, positive nucleus and negative electrons revolving in orbit around the nucleus

Bohr Atom

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Basic Atomic Particles

Proton

Positive charge

Represents the Atomic Z#

Distinguishes elements by number of protons in the nucleus

Change the Z#, change the element!

Basic Atomic Particles Neutron

Neutral charge

Stability of nucleus

Serve in the role in radioactive atoms (isotopes)

Electron

Negative charge

Electrical stability maintained through equal number of protons and electrons

Atomic Mass Unit (amu) Unit used to measure atomic mass.

It is not a metric unit, based on the standard of the carbon-12 atom.

The equivalent mass in kilograms notes the small size of an atomic mass unit

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Electrons Electrons (-) charge

Subatomic particle

Small quantity of mass

Located outside nucleus in orbital shells

Stable atoms have equal electrons as protons

Electron shells Ordered from the first shell (K) to

the last shell (Q)

Electron Shells Represent the energy levels

Maximum number of electrons in each shell based upon 2n2

K shell: Shell #1 = 2 electrons (innermost)

L shell: Shell #2 = 8 electrons (2)(2)2

M shell: Shell #3 = 18 electrons (2)(3)2

Q shell: Shell # 7 = 98 electrons (2)(7)2

A maximum of 8 electrons may comprise the outermost shell of any atom (valence shell)

Electron Shell Maximum

Factoid: The largest naturally occurring atom, uranium, has a total of 92 electrons in its

seven shells. Even in this atom, shells 5, 6, and 7 are not completely filled.

Shell

Number

Principle

Quantum #

Shell Symbol Number of

Electrons

1 K 2

2 L 8

3 M 18

4 N 32

5 O 50

6 P 72

7 Q 98

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Forces Nuclear Binding Energy

Holds protons and neutrons together in the nucleus

Sum of the strong nuclear forces that attract

and pull the protons and neutrons together in the nucleus

Measure of the amount of energy needed to

split the atom If a particle shot at the atom strikes the nucleus with

the energy equal to the nucleus's binding energy, the atom could break up or "split."

Forces Centripetal force

Maintains electron in orbit preventing it from flying away from the nucleus

Center seeking force Balances the force created by the electron velocity

Forces

Centrifugal force

Maintains electron at a distance from the nucleus while moving around the nucleus

Out from center force

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Forces Electron Binding Energy (BE)

Maintains electrons in their shells

Dependent upon:

Proximity to nucleus

Higher BE closer to nucleus

Total # electrons in the atom

Higher BE in larger atoms

Most of the BE comes from the force of attraction between the electrons and

protons

Electron Binding Energy (Eb)

Energy needed to eject electron from atom

TUNGSTEN

(Eb)Comparison

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Electron Binding Energy

CHARGE & IONS

Neutral atoms: equal # of electrons and

protons

Balanced or stable

If an electron is added or removed the atom is no longer neutral: it becomes electrically charged.

Negative ion - An atom with an extra electron

Positive ion - - An atom that has one fewer electrons than protons

IONS

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IONS

Ionization Adding or removing an electron from its

shell

An atom in which this has occurred is called an ion.

If an electron is added, termed a negative ion (-1 charge)

If an electron is removed, termed a positive ion (+1 charge)

Ionization

Positive or Negative Ion??

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ATOMIC NUMBER & ATOMIC MASS NUMBER

ATOMIC NUMBER ATOMIC MASS NUMBER

Definition: Equal to the number of protons in

the nucleus of an atom

Elements Z number

Definition: Equal to the number of protons and

neutrons in an atom

Elements A number

May be measured using amu (atomic

mass unit)

ATOMIC MASS NUMBER &

ATOMIC NUMBER

Both the A number (atomic mass number)

and Z number (atomic number) are often

given to represent an element Y as follows:

A

Y Z

Periodic Table of Elements Arranged based on increasing atomic #

Groups are vertical columns

Represent same # electrons in outermost shell Similar chemical characteristics

Group I, II: Light metals Groups III VI: Non-metals Group VII: Halogens Group VIII: Noble gases

Periods are horizontal rows

Represent the total number of electron shells

Interpretation of Table

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Periodic Table of Elements

Non-Metals

Periodic Table of Elements http://www.periodicvideos.com/#

Periodic Table of Elements No set ratio of neutrons to protons in atoms

Larger and more stable the atom, the higher its ratio of neutrons to protons.

Many stable atoms with a low atomic number have about the same number of neutrons

and protons.

Heavier elements may have almost twice as many neutrons as protons.

greater strong nuclear force is needed

to help stabilize such atoms to keep the

nucleus from breaking up.

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Nuclear arrangements

Isotope

Atoms with same atomic number Unstable isotopes often have a deficient or excess

number of neutrons. This causes them to spontaneously change from one element to another.

Considered radioactive, referred as radioisotopes

Isobar

Atoms with same atomic mass

Isotone

Atoms with same neutron number

Nuclear Arrangements

Nuclear Arrangements

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Combination of Atoms

Atoms of different elements may combine to form molecules

Ionic Bonding occurs when an electron from one atom

transfers to another atom

Sodium Chloride (NaCl)

Combination of Atoms Covalent Bonding occurs when two atoms share

some of the same electrons which revolve around

both nuclei Water (H2O)

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