chapter_9.pptx

8/10/2019 Chapter_9.pptx

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Classifying the Elements: The Per iodic

Law and the Periodic Table

1869 Dimitri MendeleevLothar Meyer

Copyright 2011 Pearson Canada Inc.

When the elements are arranged in order of increasing

atomic mass, certain sets of properties recur periodically.


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The Periodic Law


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Mendeleevs Periodic Table

1871

= 44

= 72= 68

= 100


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Mendeleevs prediction


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X-Ray Spectra

Moseley 1913

X-ray emission is

explained in terms of

transitions in which e-

drop into orbits close

to the atomic nucleus. Correlated frequencies

to nuclear charges.

= A (Zb)2

Used to predict newelements (43, 61, 75)

later discovered.


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The Periodic tableAlkali Metals

Alkaline Earths

Transition Metals

Halogens

Noble Gases

Lanthanides and Actinides

Main Group

Main Group


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Metals and Nonmetals and Their I ons

Metals

Good conductors of heat and electricity.

Malleable and ductile.

Moderate to high melting points.

NonmetalsNonconductors of heat and electricity.

Brittle solids.

Some are gases at room temperature.

Metalloids

Metallic and non-metallic properties


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Main-Group Metal I ons

Metals tend to lose electrons to attain noblegas electron configurations.


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Main-Group Nonmetal I ons

Nonmetals tend to gain electrons to attain noble-gas

electron configurations


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Sizes of Atoms and I ons


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Screening and Penetration

Zeff= ZS

En= - RH n2

Zeff2


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Screening and Penetration

FIGURE 9-4


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Cationic Radii


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Anionic Radii


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I onic Radius

Cations are smaller than the atoms from which they are

formed.

For isoelectronic cations, the more positive the ionic charge,

the smaller the ionic radius.

Anions are larger than the atoms from which they are

formed. For isoelectronic anions, the more negative the

charge, the larger the ionic radius.


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Atomic and I onic Radii


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I onization Energy

Mg(g) Mg+(g) + e- I1= 738 kJ

Mg+(g) Mg2+(g) + e- I2= 1451 kJ

I = RH n2

Zeff2

Ionization energies decrease as atomic radii increase.


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F irst I onization Energy


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I2(Mg) vs. I3 (Mg)

7733

1451

I1(Mg) vs. I1(Al)

737.7 577.6

I1(P) vs. I1(S)

1012 999.6


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Electron Aff ini ty

F(g) + e- F-(g) EA = -328 kJ

F(1s22s22p5) + e- F-(1s22s22p6)

Li(g) + e- Li-(g) EA = -59.6 kJ


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F irst Electron Aff ini ties


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Second Electron Aff inities

O(g) + e- O-(g) EA = -141 kJ

O-(g) + e- O2-(g) EA = +744 kJ


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Magnetic Properties

Diamagnetic atoms or ions:

All e-are paired.

Weakly repelled by a magnetic field.

Paramagnetic atoms or ions:

Unpaired e-.

Attracted to an external magnetic field.


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Paramagnetism


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Periodic Properties of the Elements


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332266

Boil ing Point

??


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Predicting compound properties


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Melting Points of Elements


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Reducing Abil i ty of Group 1 and 2 Metals

2 K(s) + 2 H2O(l) 2 K++ 2 OH-+ H2(g)

Ca(s) + 2 H2O(l) Ca2++ 2 OH-+ H2(g)

I1= 419 kJ

I1= 590 kJ

I2= 1145 kJ


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Oxidizing Abil i ties of the Halogens

2 Na + Cl2 2 NaCl

Cl2+ 2 I- 2 Cl- + I2


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Acid Base Nature of Element Oxides

Basic oxides or base anhydrides:

Li2O(s) + H2O(l) 2 Li+(aq) + 2 OH-(aq)

Acidic oxides or acid anhyhydrides:

SO2(g) + H2O(l) H2SO3(aq)

Na2O and MgO yieldbasicsolutions

Cl2O, SO2and P4O10yield acidicsolutions SiO2dissolves in strong base, acidicoxide.

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