CHEM 105 Chapter 5 Quiz Flashcards
metal and nonmetal atoms form ? bonds
ionic
nonmetal and nonmetal atoms form ? bonds
covalent
metal and metal atoms form ? bonds
metallic
electronegativity ? down a period (L to R) and ? down a group (top to bottom)
increases down a period and decreases down a group
? is the most EN element (4.0)
Fluorine
? is the least EN element (0.7)
Francium
ΔEN small (0-0.4)
covalent (nonpolar covalent if not 0)
ΔEN = 0
pure covalent (equal sharing of the atoms in the bond)
ΔEN intermediate (0.4-2.0)
polar covalent (unequal sharing of electrons b/w the atoms in the bond)
ΔEN large (2.0+)
ionic
dipole moment (μ)
a measure of bond polarity; directly proportional to the size of the partial charges (q) and directly proportional to the distance (r) between them
μ = qr
measured in Debyes (D)
generally, the more electrons two atoms share and the larger the atoms are, the (smaller/larger) the dipole moment
larger
percent ionic character
the percent of a bond’s measured dipole moment compared to what it would be if the electrons were completely transferred (indicates the degree to which to the electron is transferred)
percent ionic character (decreases/increases) with ΔEN
increases
steps to drawing Lewis structures
- add up valence e-s
- choose central atom (lower EN) and draw one bond to each terminal atom
- fill in octet (or duet, in the case of H), for each terminal atom
- add remaining e-s to central atom (if any)
- check the numbers and the octets
resonance
used when two or more valid Lewis structures can be drawn for the same compound ()
formal charge
an electron bookkeeping system that allows us to discriminate between alternative Lewis structures; the different between the number of valence electrons and the number of electrons in the structure
better Lewis structures have
fewer formal charges, smaller formal charges, and the negative formal charge on the more EN atom
formal charge rules
- sum in neutral atom must be zero
- sum in an ion must equal the charge of the ion
- small (or zero) formal charges on individual atoms are better than large ones
- when formal charge cannot be avoided, negative formal charge should reside on the most EN atom