Chapter9LEcturepart2

Chapter9LEcturepart2 - Chapter 9 and 10: Covalent Bonding...

Info iconThis preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
6 Copyright: 2010 Prof. Magde Chapter 9 and 10: Covalent Bonding Lewis Dot Diagrams • Prof. G. N. Lewis worked through the first half of the 20 th century. He is the first person we have come across who did his work in California. He died in his research lab while working with cyanide, if I recall. • Like Bohr, but unlike most others, Lewis was not only a great scientist/chemist but also a great builder-manager-administrator. He had a huge effect on UC and all California. • First idea: Valence electrons are important. Let’s represent them with dots. • We will use Hund’s rule to an extreme and place the dots separately when we can. • Examples are on the next slide
Background image of page 1

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

View Full DocumentRight Arrow Icon
6 Copyright: 2010 Prof. Magde Chapter 9: Lewis Dot Diagrams Later when we refer to group or column numbers, we mean these numbers, from 1 to 8. We need them for formal charges.
Background image of page 2
6 Copyright: 2010 Prof. Magde Chapter 9: Lewis Dot Diagrams • The second idea is that closed shells are good things. We saw this for ionization energy and electron affinity, and we saw it again for ions. • Empty shells are good for cation (+) ions. • Full octets are good for (-) anions. • The ions can be happy by themselves. • For molecules, the atoms have to cooperate to get complete shells, which means mostly complete octets: • When the electrons are shared between two atoms, we call them a bond and usually replace the two dots with a line. • The single dot for Cl can go on any side.
Background image of page 3

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

View Full DocumentRight Arrow Icon
6 Copyright: 2010 Prof. Magde Chapter 9: Lewis Dot Diagrams • Hydrogen does not need an octet; in fact, it can only have a duet: • Why is HCl not an ionic solid? • You can have 1 or 2 or 3 electron pairs between atoms to get the octets:
Background image of page 4
6 Copyright: 2010 Prof. Magde Chapter 9: Lewis Dot Diagrams • The point is that these diagrams do reproduce what is observed for atoms bonding together to make molecules. • In fact, the double and triple bonded molecules are bonded more strongly. • When the octets are all satisfied, there is no tendency to make any larger structure. All the “permanent” gases at room T have nice octets: He, Ar, and the other noble gases, O 2 , N 2 , F 2 , Cl 2 . Larger molecules like Br 2 may be liquid at room T but they turn to gases at only slightly higher T. • The diagrams are intended for even numbers of electrons (and help explain why most molecules do have even numbers of electrons), but if you have to work with an odd-electron molecule, just stick the extra dot somewhere:
Background image of page 5

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

View Full DocumentRight Arrow Icon
6 Copyright: 2010 Prof. Magde Chapter 9: Lewis Dot Diagrams • You can make bigger molecules. Here is ethyl alcohol: • A non-bonding pair, like the two pairs on
Background image of page 6
Image of page 7
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 01/12/2011 for the course CHEM 6A taught by Professor Pomeroy during the Fall '08 term at UCSD.

Page1 / 21

Chapter9LEcturepart2 - Chapter 9 and 10: Covalent Bonding...

This preview shows document pages 1 - 7. Sign up to view the full document.

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