Chapter 9 Flashcards

(23 cards)

1
Q

why do chemical bonds form

A

they lower potential energy between charged particles that compose atoms

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2
Q

ionic bond

A

metal + nonmetal bond and the metal transfer 1 or more electrons to nonmetal

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3
Q

covalent bond

A

nonmetal + nonmetal; electrons are shared, not transferred

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4
Q

metallic bonding

A

metal + metal; simplest form is electron sea model where atoms in metal lattice pool their valence electrons and are delocalized over the entire metal

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5
Q

lattice energy

A

energy associated with formation of crystalline lattice; always exothermic so lattice energy is always negative
ionic radii increase as we move down the column

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6
Q

ionic bond properties

A

ionic solids:
high melting points
nonconductive
solutions of ionic compounds conduct electricity

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7
Q

bond length and strength

A

double bond is shorter and stronger than single

triple bond is shorter and stronger than double

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8
Q

difference in direction and melting point for covalent vs ionic

A

covalent = shares a specific pair of electrons
ionic = non directional and share an array of ions
molecular compounds have lower melting and boiling points than ionic compounds

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9
Q

electronegativity

A

atom’s ability to attract electrons in a chemical bond

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10
Q

periodic trends for electronegativity

A

increases across period
decreases down a column
flourine = most electronegative
Francium = lease electronegative

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11
Q

degree of polarity depends on..

A

difference between electronegativity of two bonding atoms

greater difference = more polar

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12
Q

dipole moment

A

measure of the separation of positive and negative charge

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13
Q

percent ionic character

A

increases with electronegativity difference
no bond is 100% ionic
ratio of bond’s actual dipole moment to dipole moment it would have if electron was completely transferred

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14
Q

resonance structures

A

two or more Lewis structures for the same molecule
write out both structures with double headed arrow between
only resonance hybrid structures exist in nature

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15
Q

formal charge

A

charge the atom would have if all bonding electrons were shared equally

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16
Q

formal charge formula

A

formal charge = # of val electrons - (# of lone pair electrons + 1/2# of bonding electrons

17
Q

how to determine most appropriate skeletal structure or resonance structure

A
  1. sum of all formal charges in neutral molecule must be 0
  2. sum of all formal charges in ion must equal charge of ion
  3. small or zero formal charges on individual atoms are better than large ones
  4. when formal charge can’t be avoided, negative formal charge should be on most electronegative atom
18
Q

odd electron species

A

molecules or electrons w/ odd # of electrons (called free radicals)
can’t write a good Lewis structure for these, but generally don’t exist in nature

19
Q

incomplete octets

A

Boron = only has 6 electrons`

20
Q

expanded octets

A

any element in third row and beyond usually have up to 12 (sometimes 14) electrons
typically octets are expanded to lower formal charge

21
Q

bond energy

A

energy required to break 1 mole of the bond in the gas phase

22
Q

exo vs endo bonds

A

break bonds = endothermic (positive)

form bonds = exothermic (negative)

23
Q

Delta H of reaction formula

A

sum of bonds broken + sum of bonds formed