Atomic Radius

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Atomic Radius

• Chemistry
• 2009

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Measures of atomic radius

• Unlike a ball, an atom doesn't have a fixed
  radius. The radius of an atom can only be found
  by measuring the distance between the nuclei of
  two touching atoms, and then halving that
  distance.

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Measuring radius

• As you can see from the diagrams, the same atom
  could be found to have a different radius
  depending on what was around it.

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Trends in atomic radius in the Periodic Table

• It is fairly obvious that the atoms get bigger as
  you go down groups. The reason - you are adding
  extra layers of electrons, extra energy levels.

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Trends in atomic radius in Periods 2 and 3

• From lithium to fluorine, the electrons are all
  in the 2-level, being screened by the 1s2
  electrons. The increasing number of protons in
  the nucleus as you go across the period pulls the
  electrons in more tightly.

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Trends in the transition elements

• Although there is a slight exception at the
  beginning of the series, the atoms are all much
  the same size.
• The size is determined by the 4s electrons. The
  pull of the increasing number of protons in the
  nucleus is more or less offset by the increasing
  number of 3d electrons.

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Atoms Radii

• K, As, Sr, O,F
• From the above atoms, which atomic has the
  largest radii?
• Which has the smallest?
• Arrange the atoms in increasing radii.
• U tube video
• http//www.youtube.com/watch?vd-hEkyYUXSofeature
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