Humboldt State University ® Department of Chemistry

Richard A. Paselk

Chem 110

General Chemistry

Summer 2006

Lecture Notes::Lec 17_22 June

© R. Paselk 2006


The Chemistry of the Elements, cont.

The Representative Elements

Hydrogen, cont.:

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

Periodic Table Demonstrations

Groups 1, Group 17 & Period Three Elements

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

  • Group IA, on the left side of the chart, is known as the alkali metals because they react with water to produce strong bases (a base is alkaline). Note that all of them are soft (cut with a butter knife), low density (Li floats on oil, Na and K float on water), very reactive metals. All of them react with water with Li<Na<K<Rb<Cs. In each case the metal gives its electron to water leaving hydroxide ion (OH- a base) and hydrogen gas. For example with sodium:

2 Na + 2 H2O 2 Na+ + 2 OH- + H2

  • Al to O
    • Note transition from metal to non-metal.
  • Group VIIA, on the right side of the chart, is known as the halogens. The halogens form acids with water, are gases at the top of the Periodic Chart and high vapor pressure liquids, then solid going down; exist as diatomic molecules (X2), and are very reactive towards metals. For example sodium reacts violently with chlorine gas to give table salt (NaCl):

2 Na + Cl2 2 NaCl

  • Group VIII is known as the Noble Gases, or sometimes the Inert Gases because until the 1960's they had no known compounds. Very unreactive. The only known compounds of the Noble gases are with very reactive elements like F and O, and even they don't form compounds with smaller Noble gases such as He and Ne.
  • Look at the elements of Period 3 (Na - Cl) Note how their properties change from metallic to non-metallic.

Group I - The Alkali Metals

Physical Properties

Properties of Group I - the Alkali Metals

Property Li Na K Rb Cs Fr
Valence-shell electron configuration 2s1 3s1 4s1 5s1 6s1 7s1
Melting point (°C) 180 98 64 39 29 -
Density (g/cm3) 0.54 0.97 0.86 1.5 1.9 -

Ionization energies - 1st & 2nd (kJ/mol)

M(s) M+(aq) + e-













Standard Reduction Potentials (V, 25°C)

M+(aq) + e- M(s)

-3.04 -2.71 -2.92 -2.92 -2.93 -
Electronegativity 1.0 0.9 0.8 0.8 0.7 0.7

Chemistry of the Alkali Metals

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Last modified 22 June 2006