Inside the Atom

1
Inside the Atom

• The Nucleus
• 5.2

2

• Whats in the nucleus?
• Atomic Number - the number of protons in the
  nucleus
• Isotopes
• Isotopes - atoms of the same element that have
  different numbers of neutrons
• Mass Number - number of neutrons plus protons in
  a nucleus
• Table Pg 136
• Nuclear Glue
• Strong nuclear force holds the protons together
  only if they are nearly touching

3

• Radioactive Decay
• Atomic nuclei are stable when they have about the
  same number of neutrons and protons
• In unstable atoms, the nucleus must release a
  particle
• Energy is given off
• Radioactive decay - the release of nuclear
  particles and energy
• Transmutation - one element changed into another
  through radioactive decay

4

• Some Isotopes Release Alpha Particles
• Smoke Detectors
• Americium-241 - undergoes transmutation by
  emitting an alpha particle
• Alpha Particle - two protons and two neutrons
• Creates electric current
• Smoke stops electric current and alarm is
  triggered
• After releasing the alpha particle Americium is
  now Neptunium

5

• Some isotopes Release Beta Particles
• Beta particle - high energy electron from the
  nucleus
• Neutron split into proton and electron
• Beta Particle is released with a large amount of
  energy
• Because there is now an extra proton, the atomic
  number and element are changed
• The mass stays the same.

6

• Half - Life
• Half-life - the amount of time required for half
  a sample of the element to decay
• Half-lives are different for each element
• Continues at a steady pace
• Carbon Dating
• Carbon-14 is used to date dead animals, plants,
  and humans
• Half-life of 5730 years
• Once dead the carbon stops replacing itself
• By comparing how much is left to how much a
  living organisms would have, the date can be
  determined

7

• Nuclear Waste Products
• Nuclear waste products are isotopes that release
  large amounts of radiation
• Contained in special waste containers
• New Elements by Transmutation
• Using a particle accelerator, scientists smash
  alpha and beta particles into existing elements
• The particles are absorbed and changes the
  existing element into a new element with a larger
  atomic number

8

• These elements do not exist in nature
• Elements 93-112 were created this way
• Tracer Elements
• Radioactive isotopes are introduced into a living
  organism
• The small half-lives prevent prolonged radiation
• Able to be followed by a device that detects
  radiation
• Used for medical diagnoses
• Pg 142 1-4