reader4 - Chemical Bonds • A chemical compound when two...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Chemical Bonds • A chemical compound when two or more atoms are bonded together by a chemical bond • Chemical bonds are formed when the electron configuration of the com- pound is more favorable than the elctron configuration of the separated atoms • The electrons can thus be viewed as the "‘glue"’ that holds the compound together. • Electrons are transferred or shared in such a way that each atom acquires an especially stable electron configuration (typically that of a noble gas). • Usually that is a noble gas configuration with eight outer shell electrons (the octet rule) Valence Electrons • Valence electrons are the electrons contained in the outermost electron shell of an atom • Only valence electrons are used for making chemical bonds Example • Carbon is number 6 in the periodic table ⇒ the neutral atom has 6 electrons • Two electrons fit in the inner shell • The remaining 4 are valence electrons • Carbon will tend to form compounds that completes its valence shell Petrucci 10.1 Covalent and Ionic Bonds Methane Petrucci 10.1 Electron Dot Diagrams • Group 1 elements all have one valence electron: . H . Na . Cs • Group 2 elements all have one valence electron: . . Be . . Mg . . Ca • and so on... . . . B . . . . C . . . . N . . . . . O . . . . . . F . . . . . . . Ne . . . . Petrucci 10.2 Lewis Structures and the Octet Rule • Sharing of a single pair of electrons produces a single covalent bond • Sharing two pairs of electrons produces a double covalent bond • Sharing three pairs of electrons produces a triple covalent bond • A pair of electrons not involved in bonding is called a lone pair Examples: Carbon dioxide Water Methane Nitrogen gas CO 2 H 2 O CH 4 N 2 H . . . . O . . . . C . . . . . . O . . H . . . . O . . . . H H . . . . C . . . . H . . N .. . . .. N . . H 2 Petrucci 10.3 Electronegativity • The ability of an atom to attract electrons toward itself in a covalent bond Polar and Non-polar Bonds Carbon dioxide Water Nitrogen gas CO 2 H 2 O N 2 . . . . O . . . . C . . . . . . O . . H . . . . O . . . . H . . N .. . . .. N . . H • Combining atoms with different electronegativities creates a polar bond • The larger the difference, the more polar the molecule Ionic and Covalent Character • A bond is never 100% ionic, even between the most and least electronega- tive element in the periodic table (CsF) there is some degree of sharing of electrons • 100% covalent bonds do exist • The higher the electronegativity difference, the larger the ionic character 3 Petrucci 3.1 Chemical Compounds • Molecular Compounds • Ionic Compounds • Network covalent solids • Metals Molecular Compounds • unit of two or more atoms held together by covalent bonds • In a covalent bond electrons are shared between atoms • Typically a small number of non-metal atoms – For example oxygen gas (O 2 ), water (H 2 O), carbon dioxide (CO 2 ) and acetone ((CH 3 ) 2 C-- O) • Molecules can be very large Macro molecule — large molecules exceeding 1000 atoms (proteins, poly-...
View Full Document

This note was uploaded on 12/04/2009 for the course CHE 15940 taught by Professor Madsen during the Spring '09 term at UC Davis.

Page1 / 22

reader4 - Chemical Bonds • A chemical compound when two...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online