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Nuclear Chemistry. Electromagnetic Radiation. A.  All objects give off radiation      1.  Radioactive           a.  unstable nuclei (more neutrons than protons)           b.  decay to different element with different atomic number       2.  Most atoms remain unchanged B.  Common properties

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electromagnetic radiation
Electromagnetic Radiation

A.  All objects give off radiation

     1.  Radioactive

          a.  unstable nuclei (more neutrons than protons)

          b.  decay to different element with different atomic number

      2.  Most atoms remain unchanged

B.  Common properties

      1.  form of energy and has no mass

      2.  travels at the speed of light (3 X 108 m/s)

      3.  can travel through a vacuum; does not need a medium like H2O

      4.  emitted by atoms as they decay or after they are energized

      5.  moves through space as packets of energy called photons

     6.  energy of photons is related to the frequency

electromagnetic radiation1
Electromagnetic Radiation

Two types of radiation:

1.  Ionizing radiation

     a.  x-rays, gamma rays

    b.  greatest energy

     c.  high frequency; short wavelength

     d.  cause particles like electrons to be ejected

     e.  exposure can cause great damage to tissues

 2.  Non-ionizing radiation

     a.  radio waves, microwaves, infrared, visible light, ultraviolet

     b.  lower energy

     c.  low frequency; long wavelength

     d.  exposure does not cause great damage to tissues

atoms
Atoms

A. atomic number = number of protons

B.  mass number = number of protons + neutrons

C. isotopes

       1.  atoms of the same element having different number of neutrons

       2.  radioisotope

                  a.  radioactive

                  b.  decays spontaneously

3.  symbol                   mass #     90

                                                               Sr

                                        Atomic #     38

4.  name

                  a.  add mass number to the name of the element

                  b.  example:  strontium-90  or Sr-90

       5.  stability of isotopes 

                  a.  stable isotopes do not decay spontaneously

b.  1500 known isotopes and  only 264 are stable

c.  85% of all isotopes are unstable

d.  can be predicted using proton to neutron ratio

                - over atomic # 83 unstable

radioactive decay
Radioactive Decay

Emission of radiation is one way that an unstable nucleus is transformed into a more stable one with less energy

radioactive decay alpha emission
Radioactive Decay:Alpha Emission

1.  alpha particle is composed of 2 protons and 2 neutrons

2.  nucleus of helium-4 atom

3.  more massive than beta particle

4.  poor penetrating power

5.  slow speed

6.  potential to cause great damage to tissue

7.  produces new particle with lower atomic # and mass #

8.  symbols of alpha particle

42He     and    α

9. example of alpha decay

22688Ra   42He   +   22286Rn

radioactive decay beta emission
Radioactive Decay:Beta Emission

1.  beta particle is an electron

2.  beta emission is equivalent to the conversion of a neutron to a proton

3.  smaller than an alpha particle

4.  moves faster and penetrates better than alpha

5.  produces new particle with higher atomic # and same mass #

6.  symbols of beta decay

0-1e      and      0-1β      and       β

7.  example of beta decay

146C   0-1e   +   147N

radioactive decay gamma
Radioactive Decay:Gamma

1.  gamma is a form of electromagnetic radiation

2.  high energy photons

3.  represents energy lost when the remaining nucleons reorganize into more stable arrangements

4.  moves at speed of light

5.  not a particle

6.  penetrates best of all types of radiation

7.  no change in particle that undergoes gamma decay

8.  symbols

00γ     and       γ

radioactive decay positron emission
Radioactive Decay:Positron Emission

1.  positron is a positive electron

2.  produces a new particle with lower atomic # and same mass #

3.  positrons have a very short life because it is annihilated when it collides with an electron, producing gamma rays

01e   +   0-1e      2 00γ

4.  example of positron  emission

3819K   3818Ar   +   0+1e

radioactive decay electron capture
Radioactive Decay: Electron Capture

1.  only type of radioactive decay in which the particle is on the reactant side of the equation (electron is consumed rather than formed)

2.  electron

3.  converts a proton to a neutron

11p   +   0-1e   10n

4.  example of electron capture

10647Ag   +   0-1e   10646Pd

artificial radioactivity bombardment reactions
Artificial Radioactivity  (Bombardment reactions)

A.  make a ‘new’ element by bombarding an element with a particle

B.  Four particles involved

     1.  target nucleus is the stable isotope that is bombarded

     2.  projectile (bullet)  is the particle fired at the target nucleus

     3.  product is the heavy nucleus produced in the reaction

     4.  ejected particle is the light nucleus or particle emitted from the reaction

     5.  example:

target nucleus   +   projectile      product nucleus   +   ejected particle

2713Al             +        42He      3015P             +        10n

nuclear energy
Nuclear Energy

In order to produce energy, an atom must lose mass.

1.  Nuclear reaction releases 1 million times more energy than chemical reaction

2.  Atoms before iron will undergo fusion to produce energy

3.  Atoms after iron will undergo fission to produce energy

4.  Iron is the “nuclear sink”  It will not undergo fusion or fission.