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Periodic TrendsPeriodic Trends
Section 4.3Section 4.3
Ionization EnergyIonization Energy
The amount of energy The amount of energy needed to remove an outer needed to remove an outer electron from a specific electron from a specific atom or ionatom or ion
Ionization EnergyIonization Energy
The TrendThe Trend
It decreases down a groupIt decreases down a groupe- shieldinge- shielding - The reduction of - The reduction of the attractive force between a + the attractive force between a + nucleus and its outermost e- b/c nucleus and its outermost e- b/c of the cancellation of some of the of the cancellation of some of the + charge by – charge of the outer + charge by – charge of the outer e-e-
Ionization EnergyIonization Energy
Ionization energy increase Ionization energy increase across a periodacross a period
Adding e- to same level & Adding e- to same level & p+ can hold it tighterp+ can hold it tighter
Atomic Radius/RadiiAtomic Radius/Radii
Atomic radiusAtomic radius
Usually determined for atoms Usually determined for atoms bonded or close togetherbonded or close together
Bond radiusBond radius – ½ the distance – ½ the distance from center to center of two from center to center of two like atoms bonded togetherlike atoms bonded together
The TrendThe Trend
Atomic radius increases as Atomic radius increases as you move down a groupyou move down a group
Due to addition of principle E Due to addition of principle E levellevel
The e- in the middle E levels The e- in the middle E levels shield the outside e- from the shield the outside e- from the force of the nucleus.force of the nucleus.
TrendTrend
Atomic radius decreases as you Atomic radius decreases as you move across a periodmove across a periodDecreases b/c of increased + Decreases b/c of increased + chargecharge–You are adding an e- and a p+, You are adding an e- and a p+,
but the e-’s are going into the but the e-’s are going into the same E level and being pulled same E level and being pulled by the p+by the p+
Atomic RadiusAtomic Radius
As charge increases, the As charge increases, the effective nuclear charge effective nuclear charge increases alsoincreases also
This pulls e- closer to the This pulls e- closer to the nucleusnucleus
Overall, this reduces the size Overall, this reduces the size of the atomof the atom
Repulsive ForcesRepulsive Forces
Eventually, the e- will get Eventually, the e- will get close and repel each otherclose and repel each other
Here, the atom doesn’t get Here, the atom doesn’t get any smallerany smaller
Similar trend for ionic radiusSimilar trend for ionic radius
Atomic RadiiAtomic Radii
ElectronegativityElectronegativity
ElectronegativityElectronegativity – a measure of the – a measure of the ability of an atom in a chemical ability of an atom in a chemical compound to attract e-’scompound to attract e-’s
The higher the e-neg, the stronger The higher the e-neg, the stronger that atom will pull e-’s from other that atom will pull e-’s from other elementselements
ElectronegativityElectronegativity
Decreases as you go down a Decreases as you go down a groupgroup
Adding principle quantum #Adding principle quantum #
+ nucleus can’t pull e- as much + nucleus can’t pull e- as much b/c of e- shieldingb/c of e- shielding
E-negE-neg
Increases across a pd.Increases across a pd.
Effective nuclear charge is Effective nuclear charge is more of a factormore of a factor
Electron AffinityElectron Affinity
The energy emitted upon the The energy emitted upon the addition of an electron to a addition of an electron to a neutral atom in the gas phase.neutral atom in the gas phase.
Becomes more negative Becomes more negative across a periodacross a periodDecreases down a groupDecreases down a groupSimilar to e-neg.Similar to e-neg.
Melting and Boiling PointMelting and Boiling Point
Not as straight forward as Not as straight forward as the other trends.the other trends.
Change as the different Change as the different orbitals begin to fillorbitals begin to fill