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CHEM 1320 Study Guide - Bromine, Lead

7 pages72 viewsFall 2013

Department
Chemistry
Course Code
CHEM 1320
Professor
Ganley

Page:
of 7
Chapter 8: Periodic Relationships Among the Elements
10/25
Development of the Periodic Table
-Early chemists: chemical properties related to atomic mass
-Newlands: Law of octaves
>Didn’t work past Ca
-Mendeleev (and Meyer): grouped by properties
>D.M. predicted element properties
-Mosely: atomic # (Z)
>Z doesn’t always go with atomic mass
>Sorting by Z makes groups make sense
Electron Configuration
-Core elements
>Inner electrons
>Filled
-Valence electrons: outermost
>Likely to be involved in reactions
>Higher energy
Same valence configuration  similar properties
Periodic Law
Same group=same valence electron configuration
Example:
Group 2:
Be 2,2
Mg2,8,2
Ca 2,2,8,2
Are the following pairs of elements similar in chemical properties?
Examples:
Cl and Br? Yes
1s2 2s2 2p5 and [Ne] 3s2 3p4 No
1s1 2s2 2p2 and [Ne] 3s2 3p2 Yes
P and S No
S and O Yes
-Representative (1A-7A)
>Incomplete s or p
-Transition metals (1B, 3B-8B)
>Incomplete d
>Number=outer e-, except 8B
-2B (no name)
>Full s and d, empty p
-f-block (Lanthanides, Actinides)
>Incomplete f
-Noble gases (8A)
>Full s and p (except He)
Elements in Equations
-Metal: empirical formula
>Sn, Cu, Ag, Nb
-Non-metals: empirical or molecular
>Empirical: C, noble gases
>Molecular: H2, N2, O2, F2, Cl2, Br2, I2, P4
>Either: S or S8
-Metalloids: empirical
>Sb, Te, Po
Representative Elements: Cations and Anions
Na [Ne]3s1 makes Na+ [Ne]
Ca [Ar]4s2 makes Ca2+ [Ar]
Al [Ne]32 3p1 makes Al3+ [Ne]
^Lose electrons to get a noble-gas configuration
H 1s1 makes H- 1s2 or [He]
F 1s2 2s2 2p5 makes F- 1s2 2s2 2p6 or [Ne]
O 1s2 2s2 2p4 makes O2- 1s2 2s2 2p6 or [Ne]
N 1s2 2s2 2p3 makes N3- 1s2 2s2 2p6 or [Ne]
^Gain electrons to get a noble-gas configuration
Na+, Al3+, F-, O2-, and N3- are all isoelectronic with Ne
What atom is isoelectronic with H-? He
Transition Metals Cations
-Electrons are always removed first from the ns orbital and then
from the (n-1)d orbitals
Examples:
Fe: [Ar]4s2 3d6 makes Fe2+: [Ar]3d6 or Fe3+: [Ar] 3d5
Mn: [Ar]4s2 3d5 makes Mn2+: [Ar]3d5
Effective nuclear charge (Zeff): “positive charge” felt by an outer
electron Zeff=Z-σ 0<σ<Z (σ=shielding constant, Z=atomic #)
Z Core Zeff Radius
Na 11 10 1 186
Mg 12 10 2 160
Al 13 10 3 143
Si 14 10 4 132
Increasing Zeff ----------------------- a period
Atomic Radius=1/2 x d
d=distance between nuclei

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