Download - Agenda Block 4
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Agenda Block 4• Attendance• Make Groups for element assignment• What did we learn last class?• What’s a trend?• Get into your groups• Discover a trend• Preform your trend• Homework-Part C and Part D
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Periodic Table Trends
WooT Get Excited!!!
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PERIODIC TRENDS:
Periodic trend -
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Atomic and Ionic Radii:
Atomic size is usually described by the radius of an atom.
Atomic radii - atomic radius usually determined by the distance between the nuclei of metal atoms in a crystal. (X-ray diffraction)
Trend-
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Ionic radii Def’n- is a measure of the size of the electron probability volume for an ion.
i.e. Charged molecules will vary in size as electrons are received or lost.
Atoms get going down a group. Atoms get moving from left to right across each period.
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Why does radius get smaller as # of electrons increases as you move across a period?
-higher atomic number --more protons --increased force of attraction causes
to move closer to the nucleus.
Why does radius get larger as you go down a group?-number of electrons -orbitals further and further from the nucleus-repulsive forces from inner electrons shields outer
electrons from attractive forces of the nucleus. ( )
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Shielding Effect
• Decrease in attraction between an
in any atom with more than one electron shell.
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Ionization Energy:Def’n- the minimum amount of energy needed to remove the most loosely bound electron from a gaseous atom to
form an .
element(g) + ionization energy -->
• Ionization energies enable scientists to predict which elements may form the positive ions in ionic substances.
• most likely to be positive ion.
• Atoms with ionization energies hold onto their electrons very tightly.
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ex Noble gases -
Alkali metals –
** ionization energies decrease as you move down a group. Ionization energies increase as you move from left to right across a period. **
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The difference between 1st, 2nd, and 3rd ionization energies is the increase in energy for every electron . (1st 2nd and 3rd)
ex Magnesium 3rd IE is considerably higher because the first 2 are valence electrons.
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Ionization energies:
-decrease as you move down a group.
-increase as you move from left to right across a period.
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Electron Affinity:
Def’n- when an electron is added to an atom to form an ion with a 1- charge.
Elements with electron affinities gain electrons easily to form negative ions (anions)
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• In general, non-metals have more negative electron affinities than the metals do.
• Non-metals release energy when they gain electrons.
• Metals have to gain energy before they gain an electron.
• ** electron affinity is more as you move up a group. EA is more as you move from left to right across a period**
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Electronegativity: Def’n- An atom’s ability to attract electrons in a chemical bond.
Fluorine is the most electronegative element (4.0). Cesium and Francium have the least electronegativities (0.7).
• Electronegativity is used to
.• Large differences in EN react to form ionic compounds
• Small difference in EN usually form covalent compounds. (sharing of electrons)
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• ** electronegativities usually from
left to right across periods and from bottom to top within groups.**
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Metallic Properties:
• General properties of metals from
right to left across periods and from top to
bottom within groups.