Humboldt State University ® Department of Chemistry

Richard A. Paselk

Chem 109 - General Chemistry - Spring 2013

Lecture Notes 23: 25 March

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Atomic Structure & Chemical Periodicity

The Periodic Table

Periodic Table of the Elements
 IA IIA IIIA IVA VA VIA VIIA VIIIA
   H  He
Li Be    B C N O F Ne
Na Mg IIIB IVB VB VI VIIB VIIIB IB IIB  Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
 Rb Sr  Y Zr Nb Mo Tc Ru Rh Pd  Ag  Cd  In Sn Sb Te I  Xe
 Cs  Ba Lu Hf Ta  W Re Os Ir  Pt Au  Hg Tl  Pb Bi Po At Rn

Recall the introduction to Chemical Periodicity in Lecture 6, including hydrogen combining ratios (LIH, BeH2, BH3, CH4, H3N, H2O, HF) and acid/base properties of oxides (basic for metals, acidic for non-metals)

Let's look at some of the elements and see what their properties are like:

2 Na + 2 H2O right arrow 2 Na+ + 2 OH- + H2

2 Na + Cl2 right arrow 2 NaCl

DEMONSTRATION: Look at Alkali metals, properties and reaction with water (Li, Na, K); Look at the elements of Period 3 (Na - Cl) Note how their properties change from metallic to non-metallic; Look at Halogens (Cl, Br, I [warm to vaporize crystals]).

Trends in Chemical Periodicity

(plots ©1994 Hanson, Harper, Paselk, & Russell)

Trends:Note the trends for

atomic size: decreases going from left right arrow right and from bottom right arrow top.

Periodic Table with Atomic Radii Trend arrow

plot of nonpolar covalent atomic radii vs. atomic number demonstrating periodicity

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© R A Paselk

Last modified 25 March 2013