periodic trends there are several important atomic characteristics that show predictable trends that...
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Periodic Trends
• There are several important atomic characteristics that show predictable trends that you should know:
–Atomic Size–Ionization Energy–Electron Affinity–Electronegativity
Atomic Size
The bonding atomic radius is defined as one-half of the distance between bonded nuclei.
++++++
++
Decreasing Atomic SizeAcross a Period
• The effect is that the more positive nucleus (+) has a greater pull on the electron cloud (-)
• The increased attraction pulls the cloud in, making atoms smaller as we move from left to right across a period
+++ +
Li Be B1s22s1 1s22s2 1s22s22p1
Li Be B
Relative Size of Atoms
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 350
Li
Na
K
Rb
Cs
La
XeKr
Zn
Cl
FHe
H
3dtransition
series
4dtransition
series
0.3
0.25
0.2
0.15
0.1
0.05
00 10 20 30 40 50 60
atomic number
atom
ic r
adiu
s
Atomic Radii
Li
Na
K
Rb
Cs
ClSPSiAl
BrSeAsGeGa
ITeSbSnIn
Tl Pb Bi
Mg
Ca
Sr
Ba
Be FONCB
1.52 1.11
1.86 1.60
2.31 1.97
2.44 2.15
2.62 2.17
0.88 0.77 0.70 0.66 0.64
1.43 1.17 1.10 1.04 0.99
1.22 1.22 1.21 1.17 1.14
1.62 1.40 1.41 1.37 1.33
1.71 1.75 1.46
1 2 13 14 15 16 17
INC
RE
AS
ES
INCREASES
Ionization EnergyAmount of energy required to remove an electron
from the ground state of a gaseous atom or ion.
Given enough energy (in the form of a photon) an electron can leave the atom completely.
The number of protons and electrons is no longer equal
IONS!!!
Ionization Energy
• Generally, as one goes across a row, it gets harder to remove an electron.
• The larger the atom is, the easier its electrons are to remove.
• Ionization energy and atomic radius are inversely proportional
Ions
• Here is a simple way to remember which is the cation and which the anion:
This is a cat-ion.This is Ann Ion.
Cats are “paw-sitive”She’s unhappy and negative.
+ +
Sizes of Ions
• Cations are smaller than their parent atoms.– The outermost
electron is removed and repulsions are reduced.
Sizes of Ions
• Anions are larger than their parent atoms.– Electrons are
added and repulsions are increased.
Ionization EnergiesP
erio
d
Group 1 18
1
2
3
4
5
6
1
2
3
4
5
6
7
Be
900
Al
578
Si
787
Ti
659
V
651
Cr
653
Mn
717
Fe
762
Co
760
Ni
737
Cu
746
Zn
906
Ga
579
Ge
762
Nb
652
Mo
684
Tc
702
Ag
731
Cd
868
In
558
Sn
709
Sb
834
Ta
761
W
770
Re
760
Hg
1007
Tl
589
Pb
716
Bi
703
N
1402
O
1314
F
1681
Cl
1251
C
1086
S
1000
Br
1140
I
1008
Na
496
K
419
Rb
403
Cs
376
Ba
503
Fr
--
Ra
509
H
1312
B
801
P
1012
As
947
Se
941
Ru
710
Rh
720
Pd
804
Te
869
Os
839
Ir
878
Pt
868
Au
890
Po
812
At
--
Li
520
Ca
590
Sc
633
Sr
550
Y
600
Zr
640
Hf
659
Mg
738
La
538
Ac
490
2
3 4 5 6 7 11 12
13 14 15 16 17
9
Ne
2081
Ar
1521
Kr
1351
Xe
1170
Rn
1038
He
2372
Rf
--
Db
--
Sg
--
Bh
--
Hs
--
Mt
--
Ds
--
Uub
--
Uut
--
Uuq
--
Uup
--
Uuu
--
Uuo
--
Mg
738
Symbol
First Ionization Energy (kJ/mol)
8 10
INCREASES
DE
CR
EA
SE
S
Electron Affinity
Electron affinity = “Love” of electrons
Energy change accompanying addition of electron to gaseous atom:
Cl + e− Cl−
Electronegativity
• Electronegativity is a measure of an atom’s attraction for another atom’s electrons.
• Is directly related to Electron Affinity
• scale that ranges from 0 to 4.– Fluorine is the most electronegative!!!!
`1
2
3
4
5
6
1
2
3
4
5
6
Electron Affinity & Electronegativity
7
Be
1.5
Al
1.5
Si
1.8
Ti
1.5
V
1.6
Cr
1.6
Mn
1.5
Fe
1.8
Co
1.8
Ni
1.8
Cu
1.9
Zn
1.7
Ga
1.6
Ge
1.8
Nb
1.6
Mo
1.8
Tc
1.9
Ag
1.9
Cd
1.7
In
1.7
Sn
1.8
Sb
1.9
Ta
1.5
W
1.7
Re
1.9
Hg
1.9
Tl
1.8
Pb
1.8
Bi
1.9
1.5 - 1.9
N
3.0
O
3.5
F
4.0
Cl
3.0
3.0 - 4.0
C
2.5
S
2.5
Br
2.8
I
2.5
2.5 - 2.9
Na
0.9
K
0.8
Rb
0.8
Cs
0.7
Ba
0.9
Fr
0.7
Ra
0.9
Below 1.0
H
2.1
B
2.0
P
2.1
As
2.0
Se
2.4
Ru
2.2
Rh
2.2
Pd
2.2
Te
2.1
Os
2.2
Ir
2.2
Pt
2.2
Au
2.4
Po
2.0
At
2.2
2.0 - 2.4
Per
iod
Actinides: 1.3 - 1.5
Li
1.0
Ca
1.0
Sc
1.3
Sr
1.0
Y
1.2
Zr
1.4
Hf
1.3
Mg
1.2
La
1.1
Ac
1.1
1.0 - 1.4Lanthanides: 1.1 - 1.3
1A
2A
3B 4B 5B 6B 7B 1B 2B
3A 4A 5A 6A 7A
8AINCREASES
DE
CR
EA
SE
S
Electronegativity
• Atomic Radii - size
• Ionization Energy – energy change when losing an e-
• Electron Affinity - energy change when gaining an e-
• Electronegativity – ability to attract e- when in a compound
Periodic Trends
Formscation!
Formsanion!
Summary of Periodic Trends
Ionic size (cations) Ionic size (anions)decreases decreases
Atomic radius decreasesIonization energy increasesElectron affinity increasesElectronegativity increases
Ato
mic
rad
ius
incr
ease
sIo
niz
atio
n e
ner
gy
dec
reas
esE
lect
ron
Aff
init
y d
ecre
ases
Ele
ctro
neg
ativ
ity
dec
reas
es
1A
2A 3A 4A 5A 6A 7A
0
CHEMISTRY 12/5/13
“Always remember that you are absolutely unique. Just like everyone else.” – Margaret Mead
DO NOW:
1.In your notes: Which atom has a larger atomic radius:
AGENDA:
1.Move seats
2.Students will be able to remember characteristics of the periodic table by completing a coloring activity
HOMEWORK:
Extra credit: Due before winter break: Bring 1 box of tissue or one hand sanitizer (worth 5 pts extra credit)
• What ion will be formed when K loses 1 e-?
K1+ (cation) • What ion will be formed when O
gains 2 e-?O2- (anion)
• Which ion above is more electronegative?
O2- (anion)
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