Transcript m5zn_2b75b651bf15359

Matter is any thing that occupies space
& has mass
 Present in three states: solid, liquid, & gas
 It could be divided into elements &
compounds
 Atoms, are the fundamental units of
elements
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The fundamental building blocks of nature; they
cannot be subdivided into smaller parts by ordinary
chemical methods, but could be broken down into
subatomic particles (electron, proton, & neutrons) by
special high-energy techniques
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The atom consists of two parts:
Nucleus (positive charged)
Electrons (negative charged)
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2.
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The identity of an atom is determined by the
composition of its nucleus & the arrangement of its
orbiting electrons.
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In 1913, Bohr imagines the atom as a
miniature solar system
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The nucleus, or dense core of the atom, is
composed of particles known as protons &
neutrons
Protons carry positive charges, whereas
neutrons carry no electrical charge.
Atoms differ from one another based on their
nuclear composition
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Mass Number is the total number of protons &
neutrons in the nucleus
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Atomic Number is the number of protons in the
nucleus
Electrons are tiny negatively charged particles
that have very little mass
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Electrons travel around the nucleus in orbits, or shells
An atom contains a maximum of seven shells, each
located at specific distance from the nucleus &
representing different energy levels
The shells are designated with the letters K-Q; the K
shell is located closest to the nucleus & has the
highest energy level
Each shell has a maximum number of electrons it can
hold
The number of shells occupied in a particular atom
depends on the number of protons in the nucleus
The amount of energy required
remove an electron from it is shell
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The electrostatic attraction between a
positively charged nucleus & its negatively
charged electrons balances the centrifugal
force of the rapidly revolving electrons &
maintains them in their orbits. Consequently,
the amount of energy required to remove an
electron from a given shell must exceed the
electrostatic force of between it & the nucleus
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The binding energy is determined by the
distance between the nucleus & the
orbiting electron & is different for each
shell
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Atoms with fewer protons have lower
binding energy while atoms with more
protons have higher binding energy
Is the process of removing an electron
from electrically neutral atom to
produce an ion pair
Ion is an atom or subatomic particle
with a positive or negative charge
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Ionization deals with electrons only &
requires sufficient energy to overcome the
electrostatic force
 The electrons in the inner shells are so tightly
bound to the nucleus that only x-rays,
gamma rays, & high-energy particles can
remove them
 In contrast, the electrons in the outer shells
have such low binding energies that they
can be easily displaced by photons of
lower energy (e.g., ultraviolet or visible light)
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Radiation that is capable of producing ions by
removing or adding an electron to an atom
A.
B.
Particulate Radiation
Electromagnetic Radiation
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It consist of nuclei or subatomic particles
moving at high velocity
1.
Electrons can be classified as beta particles or
cathode rays.
Alpha particles are emitted from the nuclei of
heavy metals & exist as two protons & neutrons
, without electrons.
Protons are accelerated particles with a
charge of +1
Neutrons are accelerated particles with no
electrical charge
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Is the movement of energy through
space as a combination of electric &
magnetic fields
 It is generated when the velocity of an
electrically charged particle is altered
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Natural Background Radiation
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Man-Made Radiation
Electromagnetic radiations are arranged
according to their energies
in what is termed the
Electromagnetic Spectrum
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Depending on their energy levels,
electromagnetic radiations can be
classified as ionizing or non-ionizing
 In the electromagnetic spectrum, only
high-energy radiations (cosmic rays,
gamma rays, & x-rays) are capable of
ionization
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Have no electrical charge
Have no mass or weight
Travel at the speed of light
Travel as both a particle & a wave
Propagate an electrical field at right angles
to path of travel
Propagate a magnetic field at right angles
to the electrical field
Have different measurable energies
(frequencies & wavelength)
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Quantum theory characterizes electromagnetic
radiation as small bundles of energy called Photons
or Quanta
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Photons are bundles of energy with no mass or
weight, which travels as wave at the speed of light &
move through space in a straight line, carrying the
energy of electromagnetic radiation
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The quantum theory of radiation has been successful
in correlating experimental data on the interaction of
radiation with atoms, the photoelectric effect, & the
production of x-rays
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The wave theory characterizes electromagnetic
radiations as waves. Such waves consist of electrical
& magnetic fields oriented in planes at right angles to
one another that oscillate perpendicular to the
direction of motion
The wave concept focuses on the properties of
velocity, wavelength, & frequency
Wave theory is more useful for considering radiation
in bulk when millions of quanta are being examined,
as in experiments dealing with refraction, reflection,
diffraction, interference, & polarization
Velocity (c) refers to the speed of the
wave
All electromagnetic radiation in vacuum
travels at 3 x 108 meters/seconds
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2.
Wavelength defined as the distance between the
crest (peak) of one wave & the crest of the next, & is
represented by Greek letter lambda (λ)
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Wavelength determines the energy & penetrating
power of the radiation; the shorter the distance
between the crests, the shorter the wavelength &
the higher the energy & ability to penetrate matter
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Wavelength is measured in nanometers (1 X 10-9
meters) for short waves (gamma rays) & in meters for
longer waves (radio waves)
3. Frequency (ƒ) of a wave refers to the
number of cycles per second
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Frequency & wavelength are inversely
related; if the frequency of the wave is
high, the wavelength will be short, & if
the frequency is low, the wavelength will
be long
Electromagnetic wave velocity, frequency, &
wavelength are related by:
C=ƒλ
The amount of energy an electromagnetic
radiation possesses depends on the
wavelength & frequency;
E= 1.24/ λ