Trends of the Periodic Table

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Trends of the Periodic Table
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Periodic Law

• If elements are organized
• according to atomic number,
• there will be a pattern of properties.

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Four Periodic Trends

• Atomic radii
• Ionic radii
• Electronegativity
• 4.Ionization energy

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Atomic Radius-half the distance between 2 nuclei

• It is basically the size of the atom.
• 
  

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The trend atomic radii DECREASE across a period

• Why?
• Each time a proton is added to the nucleus, the
  negative electrons feel a greater attraction to
  the positively-charged nucleus.
• Stronger nuclear force moving across period.

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Decreasing getting smaller!
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Trend atomic radiiINCREASE down a group

• Why?
• Energy levels are being added.

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• The farther the electrons
• from the nucleus, the larger
• the atomic radii.
• This increases the size of the atom.

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Atomic radii INCREASEdown a group!
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Try these . . .

• Which element has the
• larger atomic radius C or F?
• ? carbon
• 2.Which element has the smaller atomic radius Ar
  or Kr?
• ? argon

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Ionic Radii

• When an atom loses or gains electrons, it forms
  an ion.
• Ion an atom with a charge ( or - )

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• What happens to an atom if it LOSES an electron?
• ? it becomes POSITIVE

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• A cation is a positive ion.

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• Positive ions (cations) are
• smaller than the atoms they
• come from because they lose
• electrons - making the atom
• smaller.

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• What happens to an atom if it GAINS an electron?
• ? It becomes more negative

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• An anion is a negatively charged ion.

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• Negative ions (anions) are
• LARGER than the atoms they
• come from because they gain
• electrons!

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The End