Periodic Trends. Describe factors that affect electron position around a nucleus. Include: nuclear...
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Transcript of Periodic Trends. Describe factors that affect electron position around a nucleus. Include: nuclear...
![Page 1: Periodic Trends. Describe factors that affect electron position around a nucleus. Include: nuclear charge, distance, shielding. Explain periodic trends.](https://reader038.fdocuments.us/reader038/viewer/2022110207/56649d845503460f94a6a7e7/html5/thumbnails/1.jpg)
Periodic Trends
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• Describe factors that affect electron position around a nucleus.
Include: nuclear charge, distance, shielding.
• Explain periodic trends using above factors.
Include: atomic / ionic radii, ionization energy, electronegativity.
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The force on an electron will affect its position around the atom. The force depends on 3 factors:
1. Nuclear charge - more protons, more attraction.
2. Distance – further apart two charges are, lower their force of attraction (Coulomb’s Law).
3. Shielding Effect - Inner electrons shield the force of the nucleus from outer electrons.
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Measured as half the distance between two nuclei when two like atoms are bonded together.
ATOMIC RADIUSSize of atoms tends to vary from substance to
substance due to different interaction.
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Decrease Across• same quantum level (same size / n value)
• increase in nuclear charge ( pulls orbitals closer)
Increase Down• new quantum level (larger size / n value)
• increased shielding (decreased force on outer e-)
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Cl:
17 e-
Na:11 p+
11 e- 17 p+
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Ion size differs from atom size.
IONIC RADIUS
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*Same* basic trend as atomic radius.
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Positive ions - smaller radii• increased proton - electron balance (lost e-)
• more nuclear charge on remaining e-
• sometimes loss of a quantum level.
Negative ions - bigger radii• decreased proton - electron balance (gain e-)
• Less nuclear charge on remaining e-
• repulsion of additional e- causes expansion.
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ClNa+ -
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Energy required to remove an electron from an atom forming an ion – energy depends on force on e-.
A(g) + energy → A+(g) + e−
There are multiple ionization energy values for each element – one for each electron being removed.
A+(g) + energy → A+2
(g) + e−
Ionization Energy
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Increases Across• increased nuclear charge (increasing p+ number)
• same quantum level
Decreases Down• new quantum levels (increased distance)
• increased shielding (decreases force on outer e-)
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ClNa+
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Na
Cs
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IE increases with each electron removed
• Increased proton-electron ratio (small change)• Less shielding (small change)• Lower quantum level – closer (BIG change)
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Electronegativity Attraction an atom has for bonding electrons.
bigger the number, the harder they pull
Periodic Trend:EN increases across the table and decreases down.
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Cl:Na:
Lower ionization energy.Lower Electronegativity.
HIGHER ionization energy.HIGHER Electronegativity.
WEAKER nuclear charge.Less attraction - large radius.
STRONGER nuclear charge.More attraction - small radius.
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The greater the electronegativity difference the more polar the bond.
Large enough difference – ionic bonds form.
+ -
Cl H
δ+δ-
Polar covalent
C HH
non-polar covalent
00
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EN Difference Bond Type Percent Ionic
less than 0.4 non-polar covalent 0% − 5%
0.4 − 1.9 polar covalent 5% − 60%
greater than 1.9 ionic > 60%
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CAN YOU / HAVE YOU?
• Describe factors that affect electron position around a nucleus.
Include: nuclear charge, distance, shielding.
• Explain periodic trends using above factors.
Include: atomic / ionic radii, ionization energy, electronegativity.