1 unit 6: chapters 11-12. pages 295-366 atomic electron configurations and periodicity
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Unit 6: Chapters 11-12. Pages 295-366 Unit 6: Chapters 11-12. Pages 295-366 ATOMIC ELECTRON ATOMIC ELECTRON
CONFIGURATIONS AND PERIODICITYCONFIGURATIONS AND PERIODICITY
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• First model of the electron behavior• Vital to understanding the atom• Does not work for atoms with
more than 1 electron
• First model of the electron behavior• Vital to understanding the atom• Does not work for atoms with
more than 1 electron
Bohr Model
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Collision of Ideas
Dalton
Thompson
Rutherford
Bohr
Newton
Maxwell
Plank
Einstein
De Broglie
Matter
Light
?
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The Photoelectric EffectDuality of Light
• Wave behavior
• Particle behavior
1905
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de Broglie’s Novel NotionLight was “known” (thought) to be a wave, but
Einstein showed that it also acts particle-like
Electrons were particles with known mass & charge
What if ……
1923
electrons behaved as waves also
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Evidence for de Broglie’s Notion
Diffraction pattern obtained with firing a beam of electrons through a crystal.
This can only be explained if the electron behaves as a wave!
Nobel Prize for de Broglie in 1929
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• Extremely small mass
• Located outside the nucleus
• Moving at very high speeds
• Have specific energy levels
• Standing wave behavior
• Extremely small mass
• Located outside the nucleus
• Moving at very high speeds
• Have specific energy levels
• Standing wave behavior
Electron Characteristics
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A baseball behaves as a particle and follows a predictable path.
BUT
An electron behaves as a wave, and its path cannot be predicted.
All we can do is to calculate the probability of the electron following a specific path.
Baseball vs Electron
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What if a baseball behaved like an electron?
Characteristic wavelength• baseball 10-34 m• electron 0.1 nm
All we can predict is…..
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Werner Heisenberg(1901-1976)
• Proposed that the dual nature of the electron places limitation on how precisely we can know both the exact location and speed of the electron
• Instead, we can only describe electron behavior in terms of probability.
The Uncertainty Principle
speedspeed
positionposition
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Erwin Schrodinger (1887-1961)
• In 1926, Austrian physicist, proposed an equation that incorporates both the wave and particle behavior of the electron
• When applied to hydrogen’s 1 electron atom, solutions provide the most probable location of finding the electron in the first energy level
• Can be applied to more complex atoms too!
Wave Equation & Wave Mechanics
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Solutions to Schrodinger’s Wave Equation
Gives the most probable location of electron in 3-D space around nucleus (probability map)
- most probable location called an
orbital
- orbitals can hold a maximum of 2 e-
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“Most Successful Theory of 20th Century”
Dalton
Thompson
Rutherford
Bohr
Newton
Maxwell
Plank
Einstein
De Broglie
Matter
Light
Schrödinger
Heisenberg
WaveMechanics
Quantum
Mechanics
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Quantum Mechanics ModelDescribes the arrangement and space
occupied by electrons in atoms
Quantum
Mechanics
Electron’s energy is quantized
Mathematics of waves to define orbitals(wave mechanics)
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Bohr Model v. Quantum Mechanics
Energy
Electron
Position/Path
Bohr Q. Mech.
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Dartboard Analogy
Suppose the size of the probability distribution is defined
as where there is a % chance of all hits being confined.
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The electron's movement cannot be known precisely.
We can only map the probability of finding the electron at various locations outside the nucleus.
The probability map is called an orbital.
The orbital is calculated to confine 90% of electron’s range.
Quantum Mechanics Model
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Arrangement of Electrons in Atoms
Arrangement of Electrons in Atoms
Electrons in atoms are arranged asElectrons in atoms are arranged as
SHELLS (n) = distance from nucleus SHELLS (n) = distance from nucleus
1, 2, 3, …1, 2, 3, …
SUBSHELLS (l) = shape of region of probabilitySUBSHELLS (l) = shape of region of probability
s, p, d, fs, p, d, f
ORBITALS (mORBITALS (mll) = orientation in space) = orientation in space
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• There is a relationship between the quantum number (n) and its the number of subshells.
Principal quantum number (n) = number of subshells
Arrangement of Electrons in Atoms
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Representing s Orbitals
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The 2s orbital is similar to the
1s orbital, but larger in size.
”Larger” means that the
highest probability for
finding the electron lies
farther out from the nucleus.
Each can hold a maximum of
electrons.
Comparison of 1s and 2s Orbitals
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Probability Maps of the Three 2p Orbitals
The 2p orbital is in the n = energy level.
There are 2p orbitals oriented in three directions.
Each orbital can hold a maximum of electrons.
The maximum number of electrons in the 2p sublevel is .
Adding all 2p orbitals would result in a sphere.
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The five 3d orbitals are generally oriented in different directions.
Adding all five orbitals, would result in a sphere.
The five orbitals, taken together, make up the d subshell of the n = 3 shell.
Each orbital can hold a maximum of two electrons.
This sublevel has a maximum of electrons.
Probability Maps of the Five 3d Orbitals
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Probability Maps of 7 f Orbitals Probability Maps of 7 f Orbitals
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Each orbital can be assigned no Each orbital can be assigned no
more than 2 electrons! And more than 2 electrons! And
each electron spins in opposite each electron spins in opposite
directions. directions.
Arrangement of Electrons in AtomsArrangement of Electrons in AtomsElectron Spin Quantum Number- mElectron Spin Quantum Number- mss
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Electron Spin Quantum Electron Spin Quantum NumberNumber
Electron Spin Quantum Electron Spin Quantum NumberNumber
DiamagneticDiamagnetic: NOT attracted to a magnetic : NOT attracted to a magnetic fieldfieldParamagneticParamagnetic: substance is attracted to a : substance is attracted to a magnetic field. Substance has magnetic field. Substance has unpaired unpaired electronselectrons..
DiamagneticDiamagnetic: NOT attracted to a magnetic : NOT attracted to a magnetic fieldfieldParamagneticParamagnetic: substance is attracted to a : substance is attracted to a magnetic field. Substance has magnetic field. Substance has unpaired unpaired electronselectrons..
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n ---> shelln ---> shell 1, 2, 3, 4, ...1, 2, 3, 4, ...
l ---> sublevell ---> sublevel s, p, d, fs, p, d, f
mmll ---> orbital ---> orbital -l ... 0 ... +l-l ... 0 ... +l
mmss ---> electron spin ---> electron spin +1/2 +1/2
and -1/2and -1/2
n ---> shelln ---> shell 1, 2, 3, 4, ...1, 2, 3, 4, ...
l ---> sublevell ---> sublevel s, p, d, fs, p, d, f
mmll ---> orbital ---> orbital -l ... 0 ... +l-l ... 0 ... +l
mmss ---> electron spin ---> electron spin +1/2 +1/2
and -1/2and -1/2
4 QUANTUM4 QUANTUMNUMBERSNUMBERS
Summary:
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Pauli Exclusion Principle- Pauli Exclusion Principle- No No two electrons in the same atom can two electrons in the same atom can
have the same set of 4 quantum have the same set of 4 quantum numbers.numbers.
Pauli Exclusion Principle- Pauli Exclusion Principle- No No two electrons in the same atom can two electrons in the same atom can
have the same set of 4 quantum have the same set of 4 quantum numbers.numbers.
Determine the quantum numbers for Determine the quantum numbers for the outer two valence electrons in the outer two valence electrons in the lithium atom.the lithium atom.
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Aufbau Principle-Electrons fill open Aufbau Principle-Electrons fill open lower energy levels sequentiallylower energy levels sequentially
lower energy to higher energy lower energy to higher energy
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Writing Electron Writing Electron ConfigurationsConfigurations
Writing Electron Writing Electron ConfigurationsConfigurations
11 s
value of nvalue of l
no. ofelectrons
spdf notationfor H, atomic number = 1
Two ways of Two ways of writing configs. writing configs. One is called One is called thethe spdf spdf notation.notation.
Two ways of Two ways of writing configs. writing configs. One is called One is called thethe spdf spdf notation.notation.
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Broad Periodic Table Classifications
• Representative Elements (main group): filling s and p orbitals (Na, Al, Ne, O)
• Transition Elements: filling d orbitals (Fe, Co, Ni)• Lanthanide and Actinide Series (inner transition elements):
filling 4f and 5f orbitals (Eu, Am, Es)
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Writing Orbital NotationsWriting Orbital NotationsWriting Orbital NotationsWriting Orbital Notations
Two ways of Two ways of writing writing configs. Other configs. Other is called theis called the orbital box orbital box notation.notation.
Two ways of Two ways of writing writing configs. Other configs. Other is called theis called the orbital box orbital box notation.notation.
Arrowsdepictelectronspin
ORBITAL BOX NOTATIONfor He, atomic number = 2
1s
21 s
Arrowsdepictelectronspin
ORBITAL BOX NOTATIONfor He, atomic number = 2
1s
21 s
One electron has n = 1, l = 0, mOne electron has n = 1, l = 0, m ll = 0, m = 0, mss = + 1/2 = + 1/2
Other electron has n = 1, l = 0, mOther electron has n = 1, l = 0, m ll = 0, m = 0, mss = - 1/2 = - 1/2
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Different subshells within the same principal shell have different energies.
The more complex the subshell, the higher its energy. This explains why the 3d subshell is higher in energy than the 4s subshell.
Energy ordering of orbitals for multi-electron atoms
Rules for Filling Orbitals
Bottom-up (Aufbau’s principle)
Fill orbitals singly before doubling up (Hund’s Rule)
Paired electrons have opposite spin (Pauli exclusion principle)
CobaltSymbol
Atomic Number
Full Configuration
Valence Configuration
Shorthand Configuration
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Orbital diagram and electron configuration for a ground
state lithium atom
Orbital diagram and electron configuration for a ground
state lithium atom
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Orbital diagram and electron configuration for a ground
state carbon atom
Orbital diagram and electron configuration for a ground
state carbon atom
Hund’s Rule- electrons in the same sublevel will spread out into their own orbital before doubling up.
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Silicon's valence electronsSilicon's valence electrons
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Selenium's valence electronsSelenium's valence electrons
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Core electrons and valence electrons in germanium
Core electrons and valence electrons in germanium
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Outer electron configuration for the elements
Outer electron configuration for the elements
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The periodic table gives the electron configuration for AsThe periodic table gives the
electron configuration for As
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Valence Electrons by GroupValence Electrons by Group
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Ion charges by groupIon charges by group
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Periodic LawPeriodic Law
All the elements in a group have the same electron configuration in their outermost shells
Example: Group 2Be 2, 2
Mg 2, 8, 2Ca 2, 2, 8, 2
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QuestionQuestion
Specify if each pair has chemical properties that are similar (1) or not similar (2):
A. Cl and Br
B. P and S
C. O and S
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General Periodic General Periodic TrendsTrends
General Periodic General Periodic TrendsTrends
1. Atomic and ionic size1. Atomic and ionic size 2. Electron affinity2. Electron affinity
3. Ionization energy 3. Ionization energy 4. Metallic Character 4. Metallic Character
Higher effective nuclear chargeElectrons held more tightly
Larger orbitals.Electrons held lesstightly.
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Effective Nuclear Charge, Effective Nuclear Charge, Z*Z*
Effective Nuclear Charge, Effective Nuclear Charge, Z*Z*
• Z* is the nuclear charge experienced by the Z* is the nuclear charge experienced by the outermost electrons.outermost electrons. Screen 8.6. Screen 8.6.
• Explains why E(2s) < E(2p)Explains why E(2s) < E(2p)• Z* increases across a period owing to Z* increases across a period owing to
incomplete shielding by inner electrons.incomplete shielding by inner electrons.• Estimate Z* by --> [ Estimate Z* by --> [ Z - (no. inner electrons) Z - (no. inner electrons) ]]• Z = number of electronsZ = number of electrons• Charge felt by 2s e- in Li Charge felt by 2s e- in Li Z* = 3 - 2 = 1 Z* = 3 - 2 = 1• Be Be Z* = 4 - 2 = 2Z* = 4 - 2 = 2• B B Z* = 5 - 2 = 3Z* = 5 - 2 = 3 and so on!and so on!
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Effective Effective Nuclear Nuclear ChargeCharge
Electron cloud for 1s electrons
Figure 8.6
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Effective Nuclear Charge, Z*Effective Nuclear Charge, Z*Effective Nuclear Charge, Z*Effective Nuclear Charge, Z*
• Atom Z* Experienced by Electrons in Valence Orbitals
• Li +1.28• Be -------• B +2.58• C +3.22• N +3.85• O +4.49• F +5.13
Increase in Increase in Z* across a Z* across a periodperiod
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Lithium Beryllium
Sodium
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Atomic Atomic SizeSize
Atomic Atomic SizeSize
•Size goes UPSize goes UP on going down on going down a group. a group. See Figure 8.9.See Figure 8.9.
•Because electrons are added Because electrons are added further from the nucleus, further from the nucleus, there is less attraction.there is less attraction.
•Size goes DOWNSize goes DOWN on going on going across a period.across a period.
•Size goes UPSize goes UP on going down on going down a group. a group. See Figure 8.9.See Figure 8.9.
•Because electrons are added Because electrons are added further from the nucleus, further from the nucleus, there is less attraction.there is less attraction.
•Size goes DOWNSize goes DOWN on going on going across a period.across a period.
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Atomic RadiiAtomic RadiiAtomic RadiiAtomic Radii Figure 8.9Figure 8.9
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Trends in Atomic SizeTrends in Atomic SizeSee Figures 8.9 & 8.10See Figures 8.9 & 8.10
0
50
100
150
200
250
0 5 10 15 20 25 30 35 40
Li
Na
K
Kr
He
NeAr
2nd period
3rd period 1st transitionseries
Radius (pm)
Atomic Number
0
50
100
150
200
250
0 5 10 15 20 25 30 35 40
Li
Na
K
Kr
He
NeAr
2nd period
3rd period 1st transitionseries
Radius (pm)
Atomic Number
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Ion SizesIon SizesIon SizesIon Sizes
Li,152 pm3e and 3p
Li+, 60 pm2e and 3 p
+Does the size goDoes the size goup or down up or down when losing an when losing an electron to form electron to form a cation?a cation?
Does the size goDoes the size goup or down up or down when losing an when losing an electron to form electron to form a cation?a cation?
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Ion SizesIon SizesIon SizesIon Sizes
• CATIONSCATIONS are are SMALLERSMALLER than the than the atoms from which they come.atoms from which they come.
Li,152 pm3e and 3p
Li +, 78 pm2e and 3 p
+Forming Forming a cation.a cation.Forming Forming a cation.a cation.
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Ion SizesIon SizesIon SizesIon Sizes
F,64 pm9e and 9p
F- , 136 pm10 e and 9 p
-Does the size go up or Does the size go up or down when gaining an down when gaining an electron to form an electron to form an anion?anion?
Does the size go up or Does the size go up or down when gaining an down when gaining an electron to form an electron to form an anion?anion?
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Ion SizesIon SizesIon SizesIon Sizes
• ANIONSANIONS are are LARGERLARGER than the than the atoms from which they come.atoms from which they come.
Forming Forming an anion.an anion.Forming Forming an anion.an anion.F, 71 pm
9e and 9pF-, 133 pm10 e and 9 p
-
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Trends in Ion SizesTrends in Ion SizesTrends in Ion SizesTrends in Ion Sizes
Figure 8.13Figure 8.13
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Ionization EnergyIonization EnergySee Screen 8.12See Screen 8.12
Ionization EnergyIonization EnergySee Screen 8.12See Screen 8.12
IE = energy required to remove an electron IE = energy required to remove an electron from an atom in the gas phase.from an atom in the gas phase.
Mg (g) + 738 kJ ---> MgMg (g) + 738 kJ ---> Mg++ (g) + e- (g) + e-
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Mg (g) + 735 kJ ---> MgMg (g) + 735 kJ ---> Mg++ (g) + e- (g) + e-
MgMg+ + (g) + 1451 kJ ---> Mg(g) + 1451 kJ ---> Mg2+2+ (g) + e- (g) + e-
MgMg2+2+ (g) + 7733 kJ ---> Mg (g) + 7733 kJ ---> Mg3+3+ (g) + e- (g) + e-
Energy cost is very high to dip into a Energy cost is very high to dip into a shell of lower n. shell of lower n. This is why ox. no. = Group no.This is why ox. no. = Group no.
Ionization EnergyIonization EnergySee Screen 8.12See Screen 8.12
Ionization EnergyIonization EnergySee Screen 8.12See Screen 8.12
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Trends in Ionization EnergyTrends in Ionization EnergyTrends in Ionization EnergyTrends in Ionization Energy
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 350
500
1000
1500
2000
2500
1st Ionization energy (kJ/mol)
Atomic NumberH Li Na K
HeNe
ArKr
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Trends in Ionization Trends in Ionization EnergyEnergy
Trends in Ionization Trends in Ionization EnergyEnergy
• IE increases across a IE increases across a period because Z* period because Z* increases.increases.
• Metals lose electrons more Metals lose electrons more easily than nonmetals.easily than nonmetals.
• Metals are good reducing Metals are good reducing agents.agents.
• Nonmetals lose electrons Nonmetals lose electrons with difficulty.with difficulty.
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Trends in Ionization Trends in Ionization EnergyEnergy
Trends in Ionization Trends in Ionization EnergyEnergy
• IE decreases down a group IE decreases down a group • Because size increases.Because size increases.
• Reducing ability generally Reducing ability generally increases down the increases down the periodic table. periodic table.
• See reactions of Li, Na, KSee reactions of Li, Na, K
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Electronegativity• A measure of the ability of an atom
that is bonded to another atom to attract electrons to itself.
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Electron AffinityElectron AffinityElectron AffinityElectron Affinity
A few elements A few elements GAINGAIN electrons electrons to form to form anionsanions..
Electron affinity is the energy Electron affinity is the energy involved when an atom gains involved when an atom gains an electron to form an anion.an electron to form an anion.
A(g) + e- ---> AA(g) + e- ---> A--(g) (g)
E.A. = ∆EE.A. = ∆E
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Electron Affinity of OxygenElectron Affinity of OxygenElectron Affinity of OxygenElectron Affinity of Oxygen
∆∆E is E is EXOEXOthermic thermic because O has because O has an affinity for an an affinity for an e-.e-.
[He] O atom
EA = - 141 kJ
+ electron
O [He] - ion
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• See Figure 8.12 and See Figure 8.12 and Appendix FAppendix F
• Affinity for electron Affinity for electron increases across a increases across a period (EA becomes period (EA becomes more negative).more negative).
• Affinity decreases down Affinity decreases down a group (EA becomes a group (EA becomes less negative).less negative).
Atom EAAtom EAFF -328 kJ-328 kJClCl -349 kJ-349 kJBrBr -325 kJ-325 kJII -295 kJ-295 kJ
Atom EAAtom EAFF -328 kJ-328 kJClCl -349 kJ-349 kJBrBr -325 kJ-325 kJII -295 kJ-295 kJ
Trends in Electron AffinityTrends in Electron AffinityTrends in Electron AffinityTrends in Electron Affinity
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Trends in Electron AffinityTrends in Electron AffinityTrends in Electron AffinityTrends in Electron Affinity
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Metallic character trends in the periodic table
Metallic character trends in the periodic table
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Metallic CharacterMetallic Character
The text links metallic character to the tendency to lose electrons in chemical reactions, and nonmetallic character to the tendency to gain electrons in chemical reactions. The metallic character trends therefore follow the ionization energy trends
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The metallic character trends explain the location of metals,
metalloids, and nonmetals
The metallic character trends explain the location of metals,
metalloids, and nonmetals
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Which is the more metallic element, Sn or Te?
Which is the more metallic element, Sn or Te?
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Which is the more metallic element, Si or Sn?
Which is the more metallic element, Si or Sn?