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Transcript
```Chapter 11
The Periodic Table
I. History of the Periodic Table
• Johann Wolfgang Döbereiner and triads
• John Newlands and the Law of Octaves
• Dmitri Mendeleev and the 1st periodic table
Mendeleev’s Periodic Table
Mendeleev’s Predictions
Predicted properties for Mendeleev’s Eka-Silicon and properties of Germanium:
Element
Eka-Silicon
(predicted 1871)
Germanium
(discovered 1886)
Atomic Weight
Density
Oxide formula
Chloride formula
72
5.5 g/cm3
EsO2
EsCl4
72.59
5.32 g/cm3
GeO2
GeCl4
Periodic Law
• Basis: Element arranged according to their
atomic masses present a clear periodicity of
properties
• Modern: The properties of elements repeat
periodically when the elements are arranged
in increasing order by their atomic numbers
Circular Periodic Table
Benfey’s Periodic Table
Physics Periodic Table
orbitals
Spiral Periodic Table
We like spirals!
Periodic system Pyramid format
Periodic system: Zmaczynski & Bayley
Periodic table in binary electron
shells layout, designed by Eric
William McPherson
Regions of the Periodic table
Representative Elements -EC
• Valence v. core electrons
Representative Elements - Ions
• Generalization of atom/ion stability
– Usually means 8 valence = octet rule
Transition Elements - EC
• Remember the exceptions to filling d orbitals
• Worksheet: Atomic Size
• Why does atomic radius decrease across a
period?
– Higher # = more protons = higher core charge
• Increased attraction between p+ & eSmaller radius
– e- pulled closer to nucleus = ????
• Why does atomic radius increase down a group?
– Valence electron shell  higher n = higher probability
of finding e- further from nucleus = ????
– Shielding by core e- = less pull on valence e- = ????
– Why?
• Lose of valence e• Results in lower n, resulting in stronger nuclear pull
– Why?
• Gain of e• Results in increased repulsion between e-
Sizes of Anions (- ions)
Sizes of Cations (+ ions)
Definition of Ionization Energy (IE)
• Ionization energy is the energy required to
remove an electron from a gaseous atom or ion.
The first or initial ionization energy or Ei of an
atom or molecule is the energy required to
remove one mole of electrons from one mole of
isolated gaseous atoms or ions. You may think of
ionization energy as a measure of the difficulty of
removing electron or the strength by which an
electron is bound. The higher the ionization
energy, the more difficult it is to remove an
electron. Therefore, ionization energy is an
indicator of reactivity.
Periodic trends – 1st Ionization Energy
exceptions
Periodic Trends – 2nd Ionization Energy
1
2
3
4
5
6
7
8
H
1312
He
2372
5250
Li
520
7297
11810
Be
899
1757
14845
21000
B
800
2426
3659
25020
32820
C
1086
2352
4619
6221
37820
47260
N
1402
2855
4576
7473
9442
53250
64340
O
1314
3388
5296
7467
10987
13320
71320
84070
F
1680
3375
6045
8408
11020
15160
17860
92010
Ne
2080
3963
6130
9361
12180
15240
Na
496
4563
6913
9541
13350
16600
20113
25666
Mg
737
1450
7731
10545
13627
17995
21700
25662
*The teal colored cells represent ionization energies where the valence
shell is now (n-1). (Why do you think there is such a large jump in the
ionization energies when the n-1 shell is now valence?)
Periodic Trends - Electronegativity
• Definition
• Increases across a period (L to R), decreases
down a group (top to bottom)
Electronegativity
• Electronegativity is a measure of the tendency
of an atom to attract a bonding pair of
electrons.
• The Pauling scale is the most commonly used.
Fluorine (the most electronegative element) is
assigned a value of 4.0, and values range
down to Cesium and Francium which are the
least electronegative at 0.7.
Electron Affinity!
Electron Affinity Definition
• the quantitative measure, usually given in
electron-volts (eV), of the tendency of an
atom or molecule to capture an electron and
to form a negative ion.
Periodic Trend for electron affinity
Periodic Trends - All
*Note: The electron affinity of an element is the energy given off when a neutral atom in
the gas phase gains an extra electron to form a negatively charged ion
Wrap-up
• Periodic Table Activity
```
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