Chem121-Chapter-8-SH

Chem121-Chapter-8-SH - Chapter 8 Basic Concepts of Chemical...

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

View Full Document Right Arrow Icon
Chapter 8 Basic Concepts of Chemical Bonding © R. Spinney 2009 Lewis Symbols of Atoms Valence shell e - are the outer most shell and are involved in chemical bonding. - they are the highest energy s and p e - - number of valence shell e - = group number - useful to show these as Lewis symbols or electron-dot symbols Lewis Symbols of Atoms (cont’d) The element symbol is used to represent the core e - and a dot for the valence shell e - Four regions around the symbol (top, right, bottom and left) correspond to the four orbitals, each can hold 2 e - i.e., Elements in the same group have the same valence shel e- configuration (see also Table 8.1)
Background image of page 1

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

View Full DocumentRight Arrow Icon
Lewis Symbols of Atoms (cont’d) Lewis Structures: G.N Lewis developed one of the earliest successful pictures of chemical bonding, stated as the octet rule : atoms tend to gain, lose or share electrons to achieve a noble gas e - configuration, 8 valence shell e - (in 4 orbitals). There are two possible types of bonds to consider, ionic and covalent. Ionic Bonding An ionic bond is an electrostatic attraction between positive & negative ions resulting from e - transfer The resulting e - configuration of both ions are those of the nearest noble gas, Ne and Kr respectively, both satisfy the octet rule. Ionic Bonding (cont’d) Note: Na is on left of PT low IE Cl is on right of PT high EA Na transfers an e - to Cl This is common for metals and nonmetals
Background image of page 2
Ionic Bonding (cont’d) The resulting compound is an array (lattice or crystal structure) of positive & negative ions packed so attractive forces between ions of opposite charges are maximized, & repulsive forces between like charges are minimized. Ionic Bonding (cont’d) The Lattice energy (LE) is a measure of the strength of attraction in the solid crystal lattice, and is defined as the energy required to separate 1 mol of solid ionic compounds into it’s gaseous ions, i.e. Ionic Bonding (cont’d) Magnitude of the LE is concentration of ionic charge, i.e. the charge density. LE is to the product of the ion charges and inversely to the distance between ions (the Σ of the ionic radii).
Background image of page 3

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

View Full DocumentRight Arrow Icon
Ionic Bonding (cont’d) The charge on the ions is the most important factor as ionic radii do not vary as much, i.e. If charges are the same then consider size of the ions: See also Table 8.2 Ionic Bonding (cont’d) The rule of removing all valence shell e - applies to all group 1A and 2A, “s-block” metals. For “p-block” metals, usually lose s and p e - to form the cation, but this may require too much E, i.e. Loss of 4 e - requires too much E it more commonly forms Pb 2+ from the loss of the 2 6p e - For groups 3A – 5A the cation charge is often (group # - 2) but Al 3+ ! Ionic Bonding
Background image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/04/2009 for the course CHEM 121 taught by Professor Wyzlouzil during the Spring '07 term at Ohio State.

Page1 / 21

Chem121-Chapter-8-SH - Chapter 8 Basic Concepts of Chemical...

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