chem 101 chapter 08 lec
TRANSCRIPT
-
8/13/2019 Chem 101 chapter 08 LEC
1/79
Chapter 8
Periodic
Properties of
the Elements
2007, Prentice Hall
Chemistry: A Molecular Approach, 1stEd.Nivaldo Tro
Roy KennedyMassachusetts Bay Community College
Wellesley Hills, MA
-
8/13/2019 Chem 101 chapter 08 LEC
2/79
Tro, Chemistry: A Molecular Approach 2
Mendeleev
order elements by atomic mass saw a repeating pattern of properties Periodic LawWhen the elements are arranged in
order of increasing atomic mass, certain sets of
properties recur periodically put elements with similar properties in the same
column used pattern to predict properties of undiscovered
elements where atomic mass order did not fit other properties,he re-ordered by other propertiesTe & I
-
8/13/2019 Chem 101 chapter 08 LEC
3/79
Tro, Chemistry: A Molecular Approach 3
Periodic Pattern
H
nm H2Oa/b
1 H2
Li
m Li2O
b
7 LiH
Na
m Na2O
b
23 NaH
Be
m/nm BeO
a/b
9 BeH2
m MgO
b
24 MgH2
Mg
nm B2O3
a
11 ( BH3)n
B
m Al2O3
a/b
27 (AlH3)Al
nm CO2
a
12 CH4
C
nm/mSiO2
a
28 SiH4
Si
nm N2O5
a
14 NH3
N
nm P4O10
a
31 PH3
P
nm O2
16 H2O
O
nm SO3
a
32 H2SS
nm Cl2O7
a
35.5 HClCl
nm
19 HF
F
a = acidic oxide, b = basic oxide, a/b = amphoteric oxide
m = metal, nm = nonmetal, m/nm = metalloid
-
8/13/2019 Chem 101 chapter 08 LEC
4/79
Tro, Chemistry: A Molecular Approach 4
Mendeleev's Predictions
-
8/13/2019 Chem 101 chapter 08 LEC
5/79
Tro, Chemistry: A Molecular Approach 5
What vs. Why
Mendeleevs Periodic Law allows us to predictwhat the properties of an element will be based
on its position on the table it doesnt explain why the pattern exists
Quantum Mechanics is a theory that explains
why the periodic trends in the properties exist
-
8/13/2019 Chem 101 chapter 08 LEC
6/79
Tro, Chemistry: A Molecular Approach 6
Electron Spin
experiments by Stern and Gerlach showed a beamof silver atoms is split in two by a magnetic field the experiment reveals that the electrons spin on
their axis
as they spin, they generate a magnetic fieldspinning charged particles generate a magnetic field
if there is an even number of electrons, about halfthe atoms will have a net magnetic field pointingNorth and the other half will have a netmagnetic field pointing South
-
8/13/2019 Chem 101 chapter 08 LEC
7/79
Tro, Chemistry: A Molecular Approach 7
Electron Spin Experiment
-
8/13/2019 Chem 101 chapter 08 LEC
8/79
Tro, Chemistry: A Molecular Approach 8
Spin Quantum Number, ms
spin quantum number describes how theelectron spins on its axisclockwise or counterclockwise
spin upor spin down
spins must cancel in an orbitalpaired
mscan have values of
-
8/13/2019 Chem 101 chapter 08 LEC
9/79
Tro, Chemistry: A Molecular Approach 9
Pauli Exclusion Principle no two electrons in an atom may have the same set of
4 quantum numbers
therefore no orbital may have more than 2 electrons,and they must have with opposite spins
knowing the number orbitals in a sublevel allows us todetermine the maximum number of electrons in thesublevelssublevel has 1 orbital, therefore it can hold 2 electrons
psublevel has 3 orbitals, therefore it can hold 6 electrons
dsublevel has 5 orbitals, therefore it can hold 10 electrons
fsublevel has 7 orbitals, therefore it can hold 14 electrons
-
8/13/2019 Chem 101 chapter 08 LEC
10/79
Tro, Chemistry: A Molecular Approach 10
Allowed Quantum Numbers
QuantumNumber
Values Number ofValues
Significance
Principal, n 1, 2, 3, ... - distance from
nucleusAzimuthal, l 0, 1, 2, ..., n-1 n shape of
orbital
Magnetic, ml -l,...,0,...+l 2l+ 1 orientation of
orbital
Spin, ms -, + 2 direction of
electron spin
-
8/13/2019 Chem 101 chapter 08 LEC
11/79
Tro, Chemistry: A Molecular Approach 11
Quantum Numbers ofHeliums Electrons
helium has two electrons
both electrons are in the first energy level
both electrons are in thesorbital of the first energy level
since they are in the same orbital, they must have opposite spins
n l ml ms
first
electron 1 0 0 +
second
electron1 0 0 -
-
8/13/2019 Chem 101 chapter 08 LEC
12/79
Tro, Chemistry: A Molecular Approach 12
Electron Configurations
the ground stateof the electron is the lowestenergy orbital it can occupy
the distribution of electrons into the various
orbitals in an atom in its ground state is called itselectron configuration
the number designates the principal energy level
the letter designates the sublevel and type of orbital
the superscript designates the number of electronsin that sublevel
He = 1s2
http://wps.prenhall.com/wps/media/objects/166/170213/ElectronConfigurationsmov.htmlhttp://wps.prenhall.com/wps/media/objects/166/170213/ElectronConfigurationsmov.html -
8/13/2019 Chem 101 chapter 08 LEC
13/79
Tro, Chemistry: A Molecular Approach 13
Orbital Diagrams we often represent an orbital as a square and the
electrons in that orbital as arrows the direction of the arrow represents the spin of the
electron
orbital with1 electron
unoccupiedorbital
orbital with2 electrons
-
8/13/2019 Chem 101 chapter 08 LEC
14/79
Tro, Chemistry: A Molecular Approach 14
Sublevel Splitting in
Multielectron Atoms the sublevels in each principal energy level of
Hydrogen all have the same energywe call orbitalswith the same energy degenerate
or other single electron systems for multielectron atoms, the energies of the sublevels
are split caused by electron-electron repulsion
the lower the value of the lquantum number, the lessenergy the sublevel hass(l= 0)
-
8/13/2019 Chem 101 chapter 08 LEC
15/79
Tro, Chemistry: A Molecular Approach 15
Penetrating and Shielding the radial distribution function shows that
the 2sorbital penetrates more deeply intothe 1sorbital than does the 2p the weaker penetration of the 2psublevel
means that electrons in the 2psublevelexperience more repulsive force, they aremore shielded from the attractive force ofthe nucleus
the deeper penetration of the 2selectronsmeans electrons in the 2ssublevelexperience a greater attractive force to thenucleus and are not shielded aseffectively
the result is that the electrons in the 2ssublevel are lower in energy than theelectrons in the 2p
-
8/13/2019 Chem 101 chapter 08 LEC
16/79
Tro, Chemistry: A Molecular Approach 16
Penetration & Shielding
-
8/13/2019 Chem 101 chapter 08 LEC
17/79
Energy
1s
7s
2s
2p
3s
3p3d
6s6p
6d
4s
4p4d
4f5s
5p
5d5f
Notice the following:1. because of penetration, sublevels within
an energy level are not degenerate2. penetration of the 4thand higher energy
levels is so strong that theirs sublevel islower in energy than the dsublevel of the
previous energy level3. the energy difference between levels
becomes smaller for higher energy levels
-
8/13/2019 Chem 101 chapter 08 LEC
18/79
Tro, Chemistry: A Molecular Approach 18
Order of Subshell Fillingin Ground State Electron Configurations
1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d
7s
start by drawing a diagramputting each energy shell ona row and listing the subshells,
(s, p, d, f), for that shell inorder of energy, (left-to-right)
next, draw arrows through
the diagonals, looping backto the next diagonaleach time
-
8/13/2019 Chem 101 chapter 08 LEC
19/79
Tro, Chemistry: A Molecular Approach 19
Filling the Orbitals with Electrons
energy shells fill from lowest energy to high subshells fill from lowest energy to highsp dfAufbau Principle
orbitals that are in the same subshell have the sameenergy
no more than 2 electrons per orbitalPauli Exclusion Principle
when filling orbitals that have the same energy, placeone electron in each before completing pairsHunds Rule
-
8/13/2019 Chem 101 chapter 08 LEC
20/79
-
8/13/2019 Chem 101 chapter 08 LEC
21/79
Tro, Chemistry: A Molecular Approach 21
2. Draw 9 boxes to represent the first 3 energy
levels sandporbitalsa) since there are only 12 electrons, 9 should be
plenty
1s 2s 2p 3s 3p
Example 8.1Write the Ground StateElectron Configuration and Orbital
Diagram and of Magnesium.
-
8/13/2019 Chem 101 chapter 08 LEC
22/79
Tro, Chemistry: A Molecular Approach 22
3. Add one electron to each box in a set, thenpair the electrons before going to the next setuntil you use all the electrons When pair, put in opposite arrows
1s 2s 2p 3s 3p
Example 8.1Write the Ground StateElectron Configuration and Orbital
Diagram and of Magnesium.
-
8/13/2019 Chem 101 chapter 08 LEC
23/79
Tro, Chemistry: A Molecular Approach 23
Example 8.1Write the Ground StateElectron Configuration and Orbital
Diagram and of Magnesium.
4. Use the diagram to write the electronconfiguration Write the number of electrons in each set as a
superscript next to the name of the orbital set
1s22s22p63s2 = [Ne]3s2
1s 2s 2p 3s 3p
-
8/13/2019 Chem 101 chapter 08 LEC
24/79
Tro, Chemistry: A Molecular Approach 24
Valence Electrons the electrons in all the subshells with the
highest principal energy shell are called thevalence electrons
electrons in lower energy shells are calledcore electrons
chemists have observed that one of the most
important factors in the way an atombehaves, both chemically and physically, isthe number of valence electrons
-
8/13/2019 Chem 101 chapter 08 LEC
25/79
Tro, Chemistry: A Molecular Approach 25
Electron Configuration of Atomsin their Ground State
Kr = 36 electrons1s22s22p63s23p64s23d104p6
there are 28 core electrons and 8 valence electrons
Rb = 37 electrons
1s22s22p63s23p64s23d104p65s1
[Kr]5s1
for the 5s1electron in Rb the set of quantum numbers isn= 5, l= 0, m
l= 0, m
s= +
for an electron in the 2p sublevel, the set of quantumnumbers is n= 2, l= 1, ml= -1 or (0,+1), and ms= - or (+)
-
8/13/2019 Chem 101 chapter 08 LEC
26/79
Tro, Chemistry: A Molecular Approach 26
Electron Configurations
-
8/13/2019 Chem 101 chapter 08 LEC
27/79
Tro, Chemistry: A Molecular Approach 27
Electron Configuration & thePeriodic Table
the Group number corresponds to the number ofvalence electrons
the length of each block is the maximumnumber of electrons the sublevel can hold
the Period number corresponds to the principalenergy level of the valence electrons
-
8/13/2019 Chem 101 chapter 08 LEC
28/79
Tro, Chemistry: A Molecular Approach 28
-
8/13/2019 Chem 101 chapter 08 LEC
29/79
Tro, Chemistry: A Molecular Approach 29
s1
s2
d1 d2 d3 d4 d5 d6 d7 d8 d9d10
s2
p1
p2
p3
p4
p5
p6
f2
f3
f4
f5
f6
f7
f8
f9
f10
f11
f12
f13
f14
f14
d1
1234
567
-
8/13/2019 Chem 101 chapter 08 LEC
30/79
Tro, Chemistry: A Molecular Approach 30
Electron Configuration fromthe Periodic Table
P = [Ne]3s23p3
P has 5 valence electrons
3p3
P
Ne123
4567
1A2A 3A 4A 5A 6A 7A
8A
3s2
-
8/13/2019 Chem 101 chapter 08 LEC
31/79
31
Transition Elements for the dblock metals, the principal energy level is one less than
valence shell one less than the Period number sometimesselectron promoted to dsublevel
4s 3d
ZnZ = 30, Period 4, Group 2B
[Ar]4s23d10
for thefblock metals, the principal energy level is twoless than valence shell two less than the Period number they really belong to
sometimes delectron in configurationEuZ = 63, Period 6[Xe]6s24f 7 6s 4f
-
8/13/2019 Chem 101 chapter 08 LEC
32/79
Tro, Chemistry: A Molecular Approach 32
Electron Configuration fromthe Periodic Table
As = [Ar]4s23d104p3
As has 5 valence electrons
As
123
4567
1A2A 3A 4A 5A 6A 7A
8A
4s2
Ar3d10
4p3
-
8/13/2019 Chem 101 chapter 08 LEC
33/79
Tro, Chemistry: A Molecular Approach 33
PracticeUse the Periodic Table to write the shortelectron configuration and orbital diagram for each of the
following Na (at. no. 11)
Te (at. no. 52)
Tc (at. no. 43)
-
8/13/2019 Chem 101 chapter 08 LEC
34/79
Tro, Chemistry: A Molecular Approach 34
PracticeUse the Periodic Table to write the shortelectron configuration and orbital diagram for each of the
following Na (at. no. 11) [Ne]3s1
Te (at. no. 52) [Kr]5s24d105p4
Tc (at. no. 43) [Kr]5s24d5
3s
5s 5p4d
5s 4d
-
8/13/2019 Chem 101 chapter 08 LEC
35/79
Tro, Chemistry: A Molecular Approach 35
Properties & Electron Configuration
elements in the samecolumn have similar
chemical and physicalproperties because they
have the same number of
valence electrons in thesame kinds of orbitals
-
8/13/2019 Chem 101 chapter 08 LEC
36/79
Tro, Chemistry: A Molecular Approach 36
Electron Configuration &Element Properties
the number of valence electrons largely determines the behaviorof an element chemical and some physical
since the number of valence electrons follows a Periodic pattern,
the properties of the elements should also be periodic quantum mechanical calculations show that 8 valence electronsshould result in a very unreactive atom, an atom that is verystableand the noble gases, that have 8 valence electrons are allvery stable and unreactive
conversely, elements that have either one more or one lesselectron should be very reactiveand the halogens are the mostreactive nonmetals and alkali metals the most reactive metals as a group
-
8/13/2019 Chem 101 chapter 08 LEC
37/79
Tro, Chemistry: A Molecular Approach 37
Electron Configuration &
Ion Charge we have seen that many metals and nonmetals
form one ion, and that the charge on that ion is
predictable based on its position on the PeriodicTableGroup 1A = +1, Group 2A = +2, Group 7A = -1,
Group 6A = -2, etc.
these atoms form ions that will result in anelectron configuration that is the same as thenearest noble gas
-
8/13/2019 Chem 101 chapter 08 LEC
38/79
Tro, Chemistry: A Molecular Approach 38
-
8/13/2019 Chem 101 chapter 08 LEC
39/79
Tro, Chemistry: A Molecular Approach 39
Electron Configuration of Anions
in their Ground State anions are formed when atoms gain enoughelectrons to have 8 valence electronsfilling thesandpsublevels of the valence shell
the sulfur atom has 6 valence electronsS atom = 1s22s22p63s23p4
in order to have 8 valence electrons, it must gain2 moreS2-anion = 1s22s22p63s23p6
-
8/13/2019 Chem 101 chapter 08 LEC
40/79
Tro, Chemistry: A Molecular Approach 40
Electron Configuration of
Cations in their Ground State cations are formed when an atom loses all itsvalence electronsresulting in a new lower energy level valence shell
however the process is always endothermic
the magnesium atom has 2 valence electronsMg atom = 1s22s22p63s2
when it forms a cation, it loses its valence electronsMg2+cation = 1s22s22p6
-
8/13/2019 Chem 101 chapter 08 LEC
41/79
Tro, Chemistry: A Molecular Approach 41
Trend in Atomic RadiusMain Group Different methods for measuring the radius of an
atom, and they give slightly different trends van der Waals radius = nonbonding
covalent radius = bonding radius
atomic radius is an average radius of an atom based onmeasuring large numbers of elements and compounds
Atomic Radius Increases down group valence shell farther from nucleus
effective nuclear charge fairly close
Atomic Radius Decreases across period (left to right) adding electrons to same valence shell
effective nuclear charge increases
valence shell held closer
-
8/13/2019 Chem 101 chapter 08 LEC
42/79
Tro, Chemistry: A Molecular Approach 42
Effective Nuclear Charge in a multi-electron system, electrons are simultaneously
attracted to the nucleus and repelled by each other outer electrons are shieldedfrom full strength of nucleus
screening effect
effective nuclear chargeis net positive charge that isattracting a particular electron
Zis nuclear charge, Sis electrons in lower energy levelselectrons in same energy level contribute to screening, but
very little
effective nuclear charge on sublevels trend,s > p > d > f
Zeffective= Z - S
-
8/13/2019 Chem 101 chapter 08 LEC
43/79
43
Screening & Effective Nuclear Charge
-
8/13/2019 Chem 101 chapter 08 LEC
44/79
Tro, Chemistry: A Molecular Approach 44
Trends in Atomic Radius
Transition Metals increase in size down the Group
atomic radii of transition metals roughly the
same size across the dblockmust less difference than across main group
elements
valence shell ns2
, not the delectronseffective nuclear charge on the ns2electrons
approximately the same
-
8/13/2019 Chem 101 chapter 08 LEC
45/79
Tro, Chemistry: A Molecular Approach 45
-
8/13/2019 Chem 101 chapter 08 LEC
46/79
Tro, Chemistry: A Molecular Approach 46
l h h
-
8/13/2019 Chem 101 chapter 08 LEC
47/79
Tro, Chemistry: A Molecular Approach 47
Example 8.5Choose theLarger Atom in Each Pair
1) Nor F,N is further left1) Nor F2) C or Ge
3) N or Al
4) Al or Ge? opposing trends
1) Nor F2) C or Ge, Ge is further down1) Nor F2) C or Ge
3) N or Al, Al is further down & left
-
8/13/2019 Chem 101 chapter 08 LEC
48/79
Tro, Chemistry: A Molecular Approach 48
Electron Configuration ofCations in their Ground State
cations form when the atom loses electronsfrom the valence shell
for transition metals electrons, may be removed
from the sublevel closest to the valence shellAl atom = 1s22s22p63s23p1Al+3ion = 1s22s22p6
Fe atom = 1s22s22p63s23p64s23d6Fe+2ion = 1s22s22p63s23p63d6
Fe+3ion = 1s22s22p63s23p63d5Cu atom = 1s22s22p63s23p64s13d10
Cu+1ion = 1s22s22p63s23p63d10
M ti P ti f
-
8/13/2019 Chem 101 chapter 08 LEC
49/79
Tro, Chemistry: A Molecular Approach 49
Magnetic Properties ofTransition Metal Atoms & Ions
electron configurations that result in unpaired electronsmean that the atom or ion will have a net magnetic fieldthis is called paramagnetismwill be attracted to a magnetic field
electron configurations that result in all paired electronsmean that the atom or ion will have no magnetic fieldthis is called diamagnetism slightly repelled by a magnetic field
both Zn atoms and Zn2+ions are diamagnetic, showingthat the two 4selectrons are lost before the 3dZn atoms [Ar]4s23d10
Zn2+ions [Ar]4s03d10
E l 8 6 W it th El t C fi ti
-
8/13/2019 Chem 101 chapter 08 LEC
50/79
Tro, Chemistry: A Molecular Approach 50
Example 8.6Write the Electron Configurationand Determine whether the Fe atom and Fe3+ion
are Paramagnetic or Diamagnetic
Fe Z = 26
previous noble gas = Ar
18 electrons
4s 3d
Fe atom = [Ar]4s23d6
unpaired electrons
paramagnetic
4s 3d
Fe3+ion = [Ar]4s03d5
unpaired electrons
paramagnetic
Trends in Ionic Radius
-
8/13/2019 Chem 101 chapter 08 LEC
51/79
Tro, Chemistry: A Molecular Approach 51
Trends in Ionic Radius Ions in same group have same charge
Ion size increases down the grouphigher valence shell, larger
Cations smaller than neutral atom; Anions biggerthan neutral atom
Cations smaller than anions except Rb+1& Cs+1bigger or same size as F-1and O-2
Larger positive charge = smaller cation for isoelectronic species
isoelectronic = same electron configuration
Larger negative charge = larger anion for isoelectronic series
-
8/13/2019 Chem 101 chapter 08 LEC
52/79
Periodic Pattern - Ionic Radius ()
Li
+1
Na
+1
K
+1
Rb
+1
Cs
+1
Be
+2
Mg
+2
Ca
+2
B
Tl
+3
+1
In
+3
+1
Ga
+3
+1
Al
+3
Sn
+4
+2
Ge
-4
Si-4
N
-3
Bi
Sb
As
-3
Te
-2
O
-2
P-3
S
-2
Se
-2
Br
-1
-1
F
I
-1
Cl
-1
H
+1-1
2A 3A 4A 5A 6A 7A
Sr
+2
Ba
+2
C
-4
Pb
+4
+2
0.68
0.97
1.33
1.47
0.31
0.66
0.99
1.13
1.40
1.84
1.98
2.21
1.33
1.81
1.96
2.20
Al
+3
+3
0.23
0.51
0.62
0.81
1A
1.69 1.35
1.71
2.12
2.22
0.71
0.840.95
-
8/13/2019 Chem 101 chapter 08 LEC
53/79
53
-
8/13/2019 Chem 101 chapter 08 LEC
54/79
Tro, Chemistry: A Molecular Approach 54
-
8/13/2019 Chem 101 chapter 08 LEC
55/79
Tro, Chemistry: A Molecular Approach 55
Ionization Energy
minimum energy needed to remove an electronfrom an atomgas state
endothermic processvalence electron easiest to remove
M(g) + IE1M1+(g) + 1 e-
M+1
(g) + IE2M2+
(g) + 1 e-
first ionization energy = energy to remove electron from
neutral atom; 2nd IE = energy to remove from +1 ion; etc.
http://wps.prenhall.com/wps/media/objects/166/170446/IonizationEnergy.htmlhttp://wps.prenhall.com/wps/media/objects/166/170446/IonizationEnergy.html -
8/13/2019 Chem 101 chapter 08 LEC
56/79
Tro, Chemistry: A Molecular Approach 56
General Trends in 1stIonization Energy
larger the effective nuclear charge on theelectron, the more energy it takes to remove it
the farther the most probable distance the
electron is from the nucleus, the less energy ittakes to remove it
1st IE decreasesdown the group
valence electron farther from nucleus 1st IE generally increasesacross the periodeffective nuclear charge increases
-
8/13/2019 Chem 101 chapter 08 LEC
57/79
Tro, Chemistry: A Molecular Approach 57
-
8/13/2019 Chem 101 chapter 08 LEC
58/79
58
E ample 8 8 Choose the Atom in Each
-
8/13/2019 Chem 101 chapter 08 LEC
59/79
Tro, Chemistry: A Molecular Approach 59
Example 8.8Choose the Atom in EachPair with the Higher First Ionization Energy
1) Al or S, Al is further left1) Al or S2) Asor Sb, Sb is further down1) Al or S2) Asor Sb
3) Nor Si, Si is further down & left
1) Al or S2) Asor Sb
3) Nor Si
4) O or Cl? opposing trends
I l iti i th T d
-
8/13/2019 Chem 101 chapter 08 LEC
60/79
Tro, Chemistry: A Molecular Approach 60
Irregularities in the Trend Ionization Energy generally increases from left
to right across a Period except from 2A to 3A, 5A to 6A
Be 1s 2s 2p
B
1s 2s 2p
N
1s 2s 2p
O
1s 2s 2p
Which is easier to remove an electron from B or Be? Why?Which is easier to remove an electron from N or O? Why?
-
8/13/2019 Chem 101 chapter 08 LEC
61/79
Tro, Chemistry: A Molecular Approach 61
Irregularities in the
First Ionization Energy Trends
Be
1s 2s 2p
B
1s 2s 2p
Be+
1s 2s 2pTo ionize Be you must break up a full sublevel, cost extra energy
B+
1s 2s 2pWhen you ionize B you get a full sublevel, costs less energy
-
8/13/2019 Chem 101 chapter 08 LEC
62/79
Tro, Chemistry: A Molecular Approach 62
Irregularities in the
First Ionization Energy Trends
To ionize N you must break up a half-full sublevel, cost extra energy
N+
1s 2s 2p
O
1s 2s 2p
N
1s 2s 2p
O+
1s 2s 2p
When you ionize O you get a half-full sublevel, costs less energy
T d i S i
-
8/13/2019 Chem 101 chapter 08 LEC
63/79
Tro, Chemistry: A Molecular Approach 63
Trends in SuccessiveIonization Energies
removal of each successiveelectron costs more energy shrinkage in size due to having more
protons than electrons
outer electrons closer to the nucleus,therefore harder to remove
regular increase in energy for each
successive valence electron large increase in energy when startremoving core electrons
-
8/13/2019 Chem 101 chapter 08 LEC
64/79
Tro, Chemistry: A Molecular Approach 64
d i l ffi i
-
8/13/2019 Chem 101 chapter 08 LEC
65/79
Tro, Chemistry: A Molecular Approach 65
Trends in Electron Affinity energy released when an neutral atom gains an electron
gas stateM(g) + 1e-M-1(g) + EA
defined as exothermic (-), but may actually beendothermic (+)
alkali earth metals & noble gases endothermic, WHY? more energy released (more -); the larger the EA generally increases across periodbecomes more negative from left to right
not absolute
lowest EA in period = alkali earth metal or noble gas
highest EA in period = halogen
-
8/13/2019 Chem 101 chapter 08 LEC
66/79
Tro, Chemistry: A Molecular Approach 66
Metallic Character
-
8/13/2019 Chem 101 chapter 08 LEC
67/79
Tro, Chemistry: A Molecular Approach 67
Metallic Character Metalsmalleable & ductile
shiny, lusterous, reflect light conduct heat and electricitymost oxides basic and ionic form cations in solution lose electrons in reactions - oxidized
Nonmetalsbrittle in solid statedull electrical and thermal insulatorsmost oxides are acidic and molecular
form anions and polyatomic anionsgain electrons in reactions - reduced
metallic character increases left metallic character increase down
-
8/13/2019 Chem 101 chapter 08 LEC
68/79
Tro, Chemistry: A Molecular Approach 68
-
8/13/2019 Chem 101 chapter 08 LEC
69/79
Tro, Chemistry: A Molecular Approach 69
Example 8 9 Choose the
-
8/13/2019 Chem 101 chapter 08 LEC
70/79
Tro, Chemistry: A Molecular Approach 70
Example 8.9Choose theMore Metallic Element in Each Pair
1) Snor Te2) P or Sb
3) Ge or In, In is further down & left
1) Snor Te2) P or Sb
3) Ge or In
4) S or Br? opposing trends
1) Snor Te, Sn is further left1) Snor Te2) P or Sb, Sb is further down
Trends in the Alkali Metals
-
8/13/2019 Chem 101 chapter 08 LEC
71/79
Tro, Chemistry: A Molecular Approach 71
Trends in the Alkali Metals atomic radius increases down the column ionization energy decreases down the column
very low ionization energiesgood reducing agents, easy to oxidizevery reactive, not found uncombined in nature react with nonmetals to form salts
compounds generally soluble in water found in seawater electron affinity decreases down the column melting point decreases down the column all very low MP for metals
density increases down the column except K in general, the increase in mass is greater than the increase
in volume
-
8/13/2019 Chem 101 chapter 08 LEC
72/79
Tro, Chemistry: A Molecular Approach 72
2 Na(s) + 2 H2O(l) 2 NaOH(aq) + H2(g)
Trends in the Halogens
-
8/13/2019 Chem 101 chapter 08 LEC
73/79
Tro, Chemistry: A Molecular Approach 73
Trends in the Halogens atomic radius increases down the column ionization energy decreases down the column very high electron affinitiesgood oxidizing agents, easy to reducevery reactive, not found uncombined in nature react with metals to form salts
compounds generally soluble in water found in seawater reactivity increases down the column react with hydrogen to form HX, acids melting point and boiling point increases down the
column density increases down the column in general, the increase in mass is greater than the increase in
volume
-
8/13/2019 Chem 101 chapter 08 LEC
74/79
Tro, Chemistry: A Molecular Approach 74
Example 8 10 Write a balanced chemical
-
8/13/2019 Chem 101 chapter 08 LEC
75/79
Tro, Chemistry: A Molecular Approach 75
Example 8.10 Write a balanced chemicalreaction for the following.
reaction between potassium metal and brominegas
K(s) + Br2(g)
K(s) + Br2(g)K+Br2 K(s) + Br2(g)2 KBr(s)
(ionic compounds are all solids at room temperature)
Example 8 10 Write a balanced chemical
-
8/13/2019 Chem 101 chapter 08 LEC
76/79
Tro, Chemistry: A Molecular Approach 76
Example 8.10 Write a balanced chemicalreaction for the following.
reaction between rubidium metal and liquidwater
Rb(s) + H2O(l)
Rb(s) + H2O(l) Rb+(aq) + OH(aq)+ H2(g)2 Rb(s) + 2 H2O(l) 2 Rb
+(aq) + 2 OH(aq)+ H2(g)
(alkali metal ionic compounds are soluble in water)
Example 8 10 Write a balanced chemical
-
8/13/2019 Chem 101 chapter 08 LEC
77/79
Tro, Chemistry: A Molecular Approach 77
Example 8.10 Write a balanced chemicalreaction for the following.
reaction between chlorine gas and solid iodineCl2(g) + I2(s)
Cl2(g) + I2(s) IClwrite the halogen lower in the column first
assume 1:1 ratio, though others also exist
2 Cl2(g) + I2(s)2 ICl(g)(molecular compounds found in all states at room
temperature)
Trends in the Noble Gases
-
8/13/2019 Chem 101 chapter 08 LEC
78/79
Tro, Chemistry: A Molecular Approach 78
Trends in the Noble Gases atomic radius increases down the column ionization energy decreases down the columnvery high IE
very unreactiveonly found uncombined in natureused as inert atmosphere when reactions with other gases
would be undersirable melting point and boiling point increases down the
column all gases at room temperaturevery low boiling points
density increases down the column in general, the increase in mass is greater than the increase in
volume
-
8/13/2019 Chem 101 chapter 08 LEC
79/79