Inorganic Lecture 9

Inorganic Lecture 9 - 1 Lecture 9 Hydrogen General...

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Unformatted text preview: 1 Lecture 9 Hydrogen General Information Different types of hydrides Hydrogen bonding Preparation of H 2 Industrial uses of H 2 Hydrates and clathrates Hydrogen The simplest atom One proton and one electron Of great importance in theoretical chemistry 1 H NMR spectroscopy We can talk about the element H in several ways 1. As the diatomic gas H 2 2. As a proton (H + ) (or oxonium ion, H 3 O + ) 3. As H-, the hydride ion 2 Some facts about Hydrogen Most abundant element in the universe 3rd most abundant on earth (after oxygen and silicon Mainly in the form of water or hydrocarbons, plant material and animal material H 2 is a colorless, odorless gas, sparingly soluble in all solvents at room temp and standard pressure The single bond in H 2 is unusually strong for a single bond in a diatomic molecule Isotopes of Hydrogen 3 isotopes of hydrogen, exhibit a greater difference in physical properties than the isotopes of any other element Protium 1 H (or H) Deuterium 2 H (or H) Tritium 3 H (or H) Found only in the upper atmosphere, radioactive N + n C + H D-D > D-H > H-H (bond strength) 1 1 2 1 3 1 14 7 1 12 6 3 1 3 H(g) H + (g) + e- The ionization energy of hydrogen is 1312 kJ/mol Too high of a H ion to exist under ordinary circumstances [H 3 O] + is an important species in aqueous solution The Hydride Ion H(g) + e- H- (g) H EA = -73 kJ/mol Alkali metal hydrides crystallize in the NaCl lattice The radius of H- is estimated to be between 130-154 pm. Approximately the same size as that of F- (133 pm) Cov radius H = 37 pm. Large increase in size for the H- ion attributed to electron- electron repulsion 4 Polar and Non-Polar E-H bond (where E = any element) Hydrides are classified according to the polarity of the E-H bond We determine the polarity or lack thereof by considering the electronegativity of H compared to the element in question There are three possibilities The hydrogen is more electronegative The we can consider the H as H- or H - The direction of the dipole is in the direction of the H The hydrogen is less electronegative Then we can consider the H as H + or H + The direction of the dipole is in the direction of the other element The hydrogen is about the same electronegativity The bond is not polar The bond is almost purely covalent (like C-H) Schematic of Polar E-H Bonds 5 HYDRIDES A term usually used to mean compounds that contain H but it really means those which have hydridic character H- or H - Saline hydrides Polar bonds, Ionic Hydrogen and an alkali metal Hydrogen and an alkaline earth metal (except Be and Mg) Transition metal hydrides Different types of bonding depending on the metal, usually ionic with H -...
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This note was uploaded on 04/07/2008 for the course CHEM 311 taught by Professor Aitken during the Spring '08 term at Duquesne.

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Inorganic Lecture 9 - 1 Lecture 9 Hydrogen General...

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