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Group 1 Ions  form a wide range of salts with ionic properties

Melting Point[]

Salts formed from alkali metals have high melting points because of the high enthalpy of formation needed to create them. These salts are very energetically stable and compact, so much energy is required to break apart the ionic lattices and create a phase change from solid to liquid.

Solubility[]

Alkali metal salts are water soluble, and solutions are conductive because ions in aqueous solution can form currents and move through the solution to continue the electrical flow.

Halide Salts[]

Halide salts are ionic and not hydrolyzed. Halide salts are ionic because of differences in electronegativity (χ >1.6 in most instances, see chart below). These salts are not hydrolyzed because though they dissolve in water, the ions are stable in aqueous solution and do not form other substances.

Ionic Character

Differences in Electronegativity between Alkali Metals and Halides

F

Cl

Br

I

At (radioactive, so not practically applicable)

Li

3.00

2.18

1.98

1.68

1.2

Na

3.05

2.23

2.03

1.73

1.3

K

3.16

2.34

2.14

1.84

1.4

Rb

3.16

2.34

2.14

1.84

1.4

Cs

3.19

2.37

2.17

1.87

1.4

Fr (radioactive, so not practically applicable)

3.3

2.5

2.3

2.0

1.5

Electronegativity values from Sargent-Welch Periodic Table of the Elements

Ionic Character increases from left to right and from top to bottom (with increasing electronegativity difference)

Oxides and Hydroxides[]

The oxides and hydroxides of group one metals are basic. Metal ions from Group I attract OH- from water to balance the positive charge; these hydroxides are Brønsted basic because the OH group dissociated in aqueous solution attracts a proton. These are strong bases because alkali hydroxides tend to dissociate into ions in aqueous solution. Alkali oxides are also basic because the large electronegativity of oxygen attracts a proton – Brønsted basicity.

Hydrides[]

the hydrides of group one metals are ionic, basic and strong reducing agents. The large differences in electronegativity between hydrogen and the alkali metals means that the hydrides are ionic (see table below). The hydrides are also basic because they can accept protons (H-, not H+ in compound). Hydrides are strong reducing agents because H- is not very stable in alkali compounds, and it is more energetically stable if it donates electrons to other substances to become H+.


Electronegativity Difference[]

Difference in Electronegativity of Hydrides

H

Li

1.22

Na

1.27

K

1.38

Rb

1.38

Cs

1.41

Fr (radioactive, so not practically applicable)

1.5

Electronegativity values from Sargent-Welch Periodic Table of the Elements

The ionic character increases down the group

Works Cited

"Astatine." Chemicool Periodic Table. Chemicool.com. 01 May 2011. Web. 5/6/2012 <http://www.chemicool.com/elements/astatine.html>.

"Francium." Chemicool Periodic Table. Chemicool.com. 24 Feb. 2011. Web. 5/6/2012 <http://www.chemicool.com/elements/francium.html>.

Housecroft, Catherine E., and Alan G. Sharpe. Inorganic Chemistry. Three ed. Harlow, England: Pearson Education Limited, 2008. 289-94. Print.

Periodic Table of the Elements. Chart. N.p.: VWR International, 2009. Web. 6 May 2012. <www.sargentwelch.com>.

Winter, Mark. WebElements Periodic Table of the Elements. The University of Sheffield, 2012. Web. 6 May 2012. <http://www.webelements.com/>.

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