Chapter 8: Flashcards
What does the Lewis structure tell us?
How atoms are connected in a molecule
Ionic Bond:
Electrostatic attraction between cation and anion, transfer of valence electrons (metal and nonmetal)
Covalent bond:
Sharing of valence electrons between nonmetals (includes metalloids)
Metalic bonds:
Dissociation of metals electrons causing a sea of shared electrons
What are the guidelines for the Lewis structure?
1) Determine the total number of valence electrons
2) Arrange the element symbols and connect with single bonds
a. atom with greatest bonding capacity in center
b. With equal bonding capacities least electronegative atom in the center
3) Complete octets of non-central atoms by adding lone pair
4) Compare valence electron numbers and attach extra valence electrons to central atom
5) Complete central atom octet
How is bonding capacity determined?
How many electrons the element needs to get an octet
What is the trend for electronegativity?
Electronegativity or electron affinity, increases left to right and decreases top to bottom
What determines the chemical activity of a molecule?
Connectivity- how the atoms connect in the specific molecule
Resonance:
When two or more equivalent Lewis structures can be drawn for one compound
Resonance:
When two or more equivalent Lewis structures can be drawn for one compound
Resonance structures:
Two or more Lewis structures with the same arrangement of atoms but different arrangement of bonding pairs of electrons
Octet Rule:
Atoms tend to lose, gain, or share electrons to obtain a set of eight valence electrons
Bonding pair of electrons:
Pair of electrons shared between two atoms in a covalent bond
Polar covalent bond:
Unequal sharing of bonding pair of electrons between two atoms resulting in uneven distribution of charge
Bond polarity:
A measure of the extent to which bonding electrons are unequally shared due to differences in electronegativity of the bonded atoms
Polar bond arrow:
Arrow points to more negative end of bond
Electronegativity:
Relative ability of an atom to attract electrons in a bond to itself
Allotropes:
Different molecular forms of the same element
How is Formal Charge found? (What is the formula)
(FC) = (number of valence electrons) - [(number of unshared e-) + 1/2 (number of e- in bonding pairs)]
Formal Charge:
Charge on atom with more or less valence electrons than it is supposed to have.
What are the criteria of the most stable resonance structures?
Formal charges equal or are close to zero
negative formal charges on the more electronegative element
Electron deficient:
Molecules with atoms having fewer than eight electrons
Free radicals:
Molecules having an odd number of electrons
Expanded valence shell:
Molecules with atoms having more than an octet
When are expended valence shells seen?
And when does this occur?
Seen for elements with Z > 12
Occurs in molecules with strongly electronegative elements (F, O Cl) and when expanded shell decreases formal charge on the central atom
Why do expended valence shells seen happen?
The electrons use empty d orbitals
