Are all atoms the same size? NaMgAlSiPSCl. So then... NaMgAlSiPSCl.

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Are all atoms the same size? NaMgAlSiPSCl

So then... NaMgAlSiPSCl

Actually... NaMg Al Si P S Cl

It has to do with Zeff NaMg Al Si P S Cl

Ya! Zeff Zeff = Z − S where –Z is the number of protons in the nucleus (atomic number)atomic number –S is the average number of electrons between the nucleus and the electron in question (the number of nonvalence electrons).

Lets review... Proton + e-

What happens if you get... Proton + Proton + e-

What happens to the # of protons as you go across Periodic Table? 1112 13 14 15 16 17

Think of protons as... Atom Proton + Proton +

So as you go across the periodic table, the nuclear charge gets stronger!

What about down a group??? Remember electrons repel Your so negative! I Hate You

So more e - shells... 11 19 You guys are pushy!

Who will get the messiest???

So more shells... Weaken the effect of the nucleus

More Protons... Strengthen the effect of the nucleus

Periodic Law Elements are arranged in order of increasing atomic #, their physical and chemical properties show a periodic (repeating) pattern.

A. Definitions 1.Nuclear Charge: number of protons 2.Shielding effect: inner electrons block outer electrons from attraction to nucleus

B. Trends How to predict trends: –1. Distance from nucleus –2. Nuclear charge (Strength of nucleus)

1.Atom size increases going down a group Why?: more energy levels (more shielding) C. Atomic Radii (size)

2.Atom size decreases going across a period left to right Why?: same amount of shells, but more protons= stronger pull C. Atomic Radii

Atomic Radii Trend 1.Size of atom 2.Period: (Left to Right)  Decreases Why? Same # shells, stronger nucleus 3.Group: (Top to Bottom)  Increases Why? More shells, more shielding

Which atom has the larger radius? BeorBa CaorBr Ba Examples yCa

Periodic Trends Practice 1. ATOMIC RADIUS Rank them from smallest to largest a. Li, C, F b. Li, Na, K c. Ge, P, O d. C, N, Al e. Al, Cl, Ga F, C, Li Li, Na, K O, P, Ge N, C, Al Cl, Al, Ga

1. Cations (+) : lose e-  gets smaller © 2002 Prentice-Hall, Inc. 2. Anions (–): gain e-  gets bigger C. Ionic Radius (ion size)

Which particle has the larger radius? S orS 2- AlorAl 3+ S 2- Examples Al

Periodic Trends Practice 2. Ionic Radius: Which species will have the smaller atomic radius? a) K + or K________ b) Ba 2+ or Ba________ c) Cl - or Cl________ d) Se 2- or Se________ e) P 3- or P 2- ________ K+K+ Ba 2+ Cl Se P 2-

XII. Periodic Trends: Ionization energy and Electronegativity

A. Ionization energy Trend 1.Energy required to remove an electron 2.Period: (Left to Right)  Increases Why? Nucleus gets stronger (Hard to steal) 3.Group: (Top to Bottom)  Decreases Why? More shells, weaker nucleus (easy to steal)

Which atom has the higher 1st Ionization Energy? N orBi BaorNe N Examples Ne

Periodic Trends Practice 2 1. IONIZATION ENERGY Rank them from lowest to highest a. Mg, Si, S b. Mg, Ca, Ba c. F, Cl, Br d. Ba, Cu, Ne e. Si, P, He Mg, Si, S Ba, Ca, Mg Br, Cl, F Ba, Cu, Ne Si, P, He

B. Electronegativity Trend 1.Ability to attract outside electrons in a bond 2.Period: (Left to Right)  Increases Why? Nucleus gets stronger (Pulls in e- better) 3.Group: (Top to Bottom)  Decreases Why? More shells, weaker nucleus (other e- further away, harder to pull in)

Periodic Trends Practice 2 2. ELECTRONEGATIVITY Rank them from lowest to highest a. Li, N, C b. C, Ne, O c. O, Si, P d. P, K, Mg e. S, He, F Li, C, N C, O, Ne Si, P, O K, Mg, P S, F, He

Summary Shielding is constant Atomic Radius decreases Ionization energy increases Electronegativity increases Nuclear charge increases Shielding increasesAtomic radius increasesIonic size increasesIonization energy decreasesElectronegativity decreases

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