topic: trends in the periodic table: ionization energy and electronegativity do now: p.13 #1-5
TRANSCRIPT
Topic: Trends in the Periodic Table: Ionization Energy and
Electronegativity
Do Now: p.13 #1-5
Trends
• more than 20 properties change in predictable way based location of elements on PT
• some properties: - anyone know where we can find these numbers?!
– Density– melting point/boiling point– atomic radius– ionization energy– electronegativity
REVIEW: How do you know if an atom gains or loses electrons?
• Think back to the Lewis structures of ions
• Atoms form ions to get a valence of 8
(or 2 for H)
• Metals tend to have 1, 2, or 3 valence electrons – It’s easier to lose them
• Nonmetals tend to have 5, 6, or 7 valence electrons– It’s easier to add some
OR
Ionization Energy
• the amount energy required to remove a valence electron from an atom in gas phase
• 1st ionization energy = energy required to remove the most loosely held valence electron (e- farthest from nucleus) = found on table S
• Cs valence electron lot farther away from nucleus than Li • electrostatic attraction much weaker so easier to steal
electron away from Cs• THEREFORE, Li has a higher Ionization energy then Cs
previous | index | next
Decreased Ionization Energy (easier to remove an electron)
Increased Ionization Energy (harder to remove an electron)
Electronegativity
• ability of atom to attract electrons in bond
• noble gases tend not to form bonds, so don’t have electronegativity values
• Unit = Pauling • Fluorine: most electronegative element = 4.0 Paulings
Dec
reas
ed I
oniz
atio
n E
nerg
y (e
asie
r to
rem
ove
an e
lect
ron)
Increased Ionization Energy (harder to remove an electron)
Decreased Electronegativity
Increased Electronegativity
Reactivity of Metals
• judge reactivity of metals by how easily give up electrons (they’re losers)
• So the easier it is to remove an electron the more reactive– Lower ionization energy = more reactive = more
metallic
Dec
reas
ed I
oniz
atio
n E
nerg
y (e
asie
r to
rem
ove
an e
lect
ron)
Increased Ionization Energy (harder to remove an electron)
Dec
reas
ed E
lect
rone
gati
vity
Increased Electronegativity
Most reactive metal = Fr(the most metallic)
More metallic
Mor
e m
etal
lic
Reactivity of Non-metals
• judge reactivity of non-metals by how easily gain electrons (they are winners)
• So the greater the affinity for electrons, the more reactive– Higher electronegativity= more reactive
Dec
reas
ed I
oniz
atio
n E
nerg
y (e
asie
r to
rem
ove
an e
lect
ron)
Increased Ionization Energy (harder to remove an electron)
Dec
reas
ed E
lect
rone
gati
vity
Increased Electronegativity
Most reactive metal = Fr(the most metallic)
More metallic
Most Reactive Nonmetal = F
Nonreactive
BACK
Nonreactive
Allotropes
• Different forms of element in same phase
– different structures and properties
• O2 and O3 - both gas phase
–O2 (oxygen) - necessary for life
–O3 (ozone) - toxic to life
• Graphite, diamond:
–both carbon in solid form