Download Week 2

Pultz 1
Test # 1 on F 14 Sept 2012 over Chapter 8 and 9
Order for writing orbitals for ground state electron configuration for Sc and higher atomic numbers:
Both are correct.
Sc: [Ar] 3d14s2 or [Ar]4s23d1
First order groups together all subshells with same principal quantum number and better represents the order
in which electrons are lost when an atom ionizes.
Second order fits better to the typical order in which orbitals fill.
Additional problems for test # 1
Chapter 8 Exercises #3, 5, 19, 25, 30, 33, 43, 51, 75, 83
Concept Assessments on p346 and p352 and p356
Practice Examples 9-1 through 9-3
Chapter 9 Exercises #17 and 19
1. Arrange Na, Mg, and K in order of increasing first ionization energy.
(a) K < Na < Mg
(b) K < Mg < Na
(c) Na < Mg < K
(d) Mg < Na < K
(e) Mg < K < Na
2. An element has the following successive ionization energies (in kJ/mol):
I1 799 I2 2422 I3 3657 I4 25 019 I5 32 660
The element is
(a) B (b) Be (c) C (d) Li (e) N
S&TY8.11
3.
Which atom has the smallest first ionization energy? Be B C N
Which atom has the smallest first ionization energy? N O F Ne
Which atom has the largest first ionization energy? Li Be B
Which atom has the largest first ionization energy? B C N O
Which atom has the largest first ionization energy? Li Na K Rb Cs
4. Choose the electron configuration that corresponds to an excited state.
(a) [Ar]3d34s2 (b) [Kr]5s1 (c) [Ar]3d54s1 (d) [Ne]3s13p6 (e) [Xe]4f145d106s2
ANSWER KEY
1. Arrange Na, Mg, and K in order of increasing first ionization energy.
(a) K < Na < Mg
(b) K < Mg < Na
(c) Na < Mg < K
(d) Mg < Na < K
2. An element has the following successive ionization energies (in kJ/mol): I1 799
25 019 I5 32 660
The element is
(a) B (b) Be (c) C (d) Li (e) N
3.
B
O
Be
N
(e) Mg < K < Na
I2 2422
I3 3657
I4
S&TY8.11
Li
4. Choose the electron configuration that corresponds to an excited state.
(a) [Ar]3d34s2 (b) [Kr]5s1 (c) [Ar]3d54s1 (d) [Ne]3s13p6 (e) [Xe]4f145d106s2
S&TY8.4
Problems for final exam: Chapter 5, p173 #65-67, 69-72
#65: An iron ore sample weighing 0.9132 g is dissolved in HCl(aq), and the iron is obtained as Fe2+(aq). This solution is then titrated with 28.72 mL
of 0.05051 M K2Cr2O7(aq), producing Fe3+ and Cr3+. Calculate the mass percent Fe in the ore sample.
Pultz 2
§9-1 Periodic Table is way of organizing physical and chemical properties of elements
The basis of the Periodic Table is the electron configurations of the elements, so we can also use the
Periodic Table to help remember the electron configurations of the elements.
In 1869 Mendeleev and Meyer independently proposed the periodic law: When elements are arranged in
order of increasing atomic mass, certain sets of properties recur periodically.
Meyer looked at molar volume
Figure 9-1
Mendeleev's insight was to leave spaces for undiscovered elements and correct some atomic massesTable 9-1
Moseley used X-ray spectra to determine nuclear charge ==> atomic number
Figure 9-2
modern periodic table: s block & p block for main group elements
d block for transition metals; f block for inner transition elements
§9-2 Metals, metalloids, and nonmetals and ions
Most metals are good conductors of heat and electricity, are malleable and ductile, and are solid at 25°C,
except Hg is liquid.
Nonmetals tend to be poor conductors of heat and electricity (except graphite electrodes) and are either
brittle solids or gases or Br2(l).
Metalloids
Going across a row, properties of main group elements change significantly since electron configuration
changes significantly.
Going across a row, properties of transition elements change some since electron configuration primarily
changes one level in (in 4th row, usually just change number of 3d electrons and keep two 4s electrons).
Within the Lanthanide or Actinide series, the number of electrons in the 4f or 5f subshell changes, and this
is two levels in from the outermost electrons in the 6s or 7s orbital; thus these elements are very similar
Noble gas electron configuration is particularly unreactive. Metal atoms tend to lose electrons in order to
obtain the nearest noble gas electron configuration. Nonmetal atoms tend to gain electrons in order to
obtain the nearest noble gas electron configuration.
Except for Al, the metals in groups 13, 14, 15, and 16 do not truly obtain a noble gas electron configuration
because they keep their d electrons (and any f electrons) added since the preceding noble gas.
Another complication for metals in groups 13, 14, 15, and 16 is that the s valence electrons are often not
lost, especially for heavier metals. Tl+ and Pb2+ and Bi3+ are more common than their higher charged ions.
Electron configurations for:
Cs+
Ba2+
BrSe2Charge on transition metal ions is often unpredictable.
Electron configuration for Sc3+,
Ti2+ and Ti3+ and Ti4+,
Fe2+ and Fe3+,
Cu+ and Cu2+
Pultz 3
§9-3 Sizes of atoms and ions and periodic trends
Atomic radii
⋅ also called covalent atomic radii because it is calculated from measurement of distance between nuclei in
Figure 9-3
covalent bonds (Cl2, diamond, etc.)
⋅ is only an estimate since orbitals decay exponentially
Trends & explain
Atomic radii decrease going L to R across a period
Figure 9-4
Atomic radii increase going down a group usually
For transition elements within a period, Zeff ≈ constant
Figure 9-8
atomic size vs. cation size
Figure 9-6
atomic size vs. anion size
Figure 9-7
For isoelectronic ions, the higher the charge, the smaller the ion:
FNa+
Mg2+
O2-
§9-4 Ionization energy
energy required to remove e- from gaseous atom/ion in ground state
depends on F ∝ q1q2/r2 = eZeff/r2
Zeff = effective nuclear charge
First Ionization Energies
depends on n & l
Figure 9-9 (note Ga & Hg) or Zumdahl 4th (every element shown)
Figure 12.35: Ionization energy
Copyright © by Houghton Mifflin Company. All rights reserved.
Note trends and effect of changing l or pairing electrons
Pultz 4
U&B 2nd edition
Pultz 5
PHHM9 Table 9-4 or Umland&Bellama2nd (more extensive & doesn’t stop with 1st core electron)
Choose an element & look at successive I.E.
1st vs 2nd vs 3rd ionization energies ==> Probable monatomic ions
Pultz 6
Umland&Bellama2nd
Electron
configurations of ions: K+, Cl-, Mn2+, Cu+, In+
form cations by removing electrons from orbital with highest n
gaseous atom gains electron
§9-5 Electron affinity: Cl(g) + e-(g) → Cl-(g)
When a gaseous halogen atom gains an electron, the reaction is highly exothermic.
· no clear trends
Figure 9-10
· confusion arising from two sign conventions; no questions except for definition
Pultz 7
§9-6 Magnetic properties
─────────────────────────────────────────────────────────────────
Property
magnetic field
electron spins
effect
diamagnetic
repelled by
paired
individual
paramagnetic
attracted by
unpaired
individual
ferromagnetic attracted by
unpaired
bulk
─────────────────────────────────────────────────────────────────
work Practice Example 9-4A on p. 358
§9-7 Trends in Periodic Table
Figure 9-8 shows sizes of atoms & ions; Ga atom is exception
First ionization energies: Prose on p. 359 and Figure 9-11 over-simplify
Ignore electron affinity in Figure 9-11
Metallic character in Figure 9-11 correlates to low electronegativity
Assume that properties change uniformly from top to bottom of a group of elements in the periodic table, for
lack of better knowledge. Use this assumption in Example 9-5 on p360.
But top element in column of the periodic table is often different from the rest:
H is nonmetal vs alkali metals; Be(OH)2 can act as an acid and a base; B is nonmetal;
HF is weak acid, but HCl & HBr & HI are strong acids.
Often have diagonal relationships!
Li
Be
B
Mg
Al
Si
correlates to electronegativity
correlates to ion size
correlates to atomic size
correlates to charge/size ratio
Be(OH)2 [+2/31pm = .06] & Al(OH)3 [+3/50pm = .06] are both amphoteric;
Mg(OH)2 [+2/65pm = .03] is basic
B(OH)3 and Si(OH)4 and As(OH)3 are acidic; Be(OH)2 and Al(OH)3 and Sb(OH)3 are amphoteric.
Note peak in melting points for third-period elements
Figure 9-13
Acid-Base nature of element oxides
CaO(s) + HOH(l) → Ca2+(aq) + 2 OH-(aq)
Li2O(s) + HOH(l) → 2 Li+(aq) + 2 OH-(aq)
Moving down a column, the elements become more metallic and their oxides become more basic.
SO3(g) + HOH(l) → H2SO4(aq)
Moving left to right in a period, elements become less metallic and their oxides become more acidic.
Amphoteric: a substance that can act as a Bronsted
/
base and as a Lewis acid. (§16-9)
Al(OH)3(s) + 3 H+(aq) → Al3+(aq) + 3 H2O(l)
Al(OH)3(s) + :OH-(aq) → [Al(OH)4]-(aq)
pages 363 and A-33 have inadequate definition for amphoteric
Figure 9-17 shows acidic, basic and amphoteric oxides of main group elements
as a Bronsted
/
base
as a Lewis acid