Transcript Lecture Eighteen

Lecture 18 © slg
Chemistry 151
TOPICS:
Review, Electronic Configuration of Atoms
• Electronic Configuration of Ions
• Magnetism
Review, Electronic Configuration of Atoms
Let’s start by doing a complete set of
configurations for lead, Pb, Z= 82
The first step: find element in periodic table noting:
a) which block (s, p, d, f)
b) which period
c) which column
Pb , Z =82, 6th period, Column 4A
1A 2A
3A 4A 5A 6A 7A 8A
1s
1s
Period 1
2s 2s
2p 2p 2p 2p 2p 2p
3s 3s
3p 3p 3p 3p 3p 3p
4s 4s
3d 3d 3d 3d 3d 3d 3d 3d 3d 3d 4p 4p 4p 4p
5s 5s
4d 4d 4d 4d 4d 4d 4d 4d 4d 4d 5p 5p 5p 5p 5p 5p
6s 6s 4f
5d 5d 5d 5d 5d 5d 5d 5d 5d 5d 6p 6p 6p 6p 6p 6p
7s 7s 5f
6p2
4p 4p
Period 6
Places last e
in subshell
Pb, Z= 82
p block
6th period
Locates shell (n# for
s,p = period #)
Column 4A
“6p2”
Locates last e in
place in orbital
6p
6p
6p
Long form, order of filling, from PT:
1s2 )2 2s2 2p6 )10 3s2 3p6 )18 4s2 3d10 4p6 )36
5s2 4d10 5p6 )54 6s2 5d1 4f14 5d9 6p2 )82
4f145d10 summarize!
Short, order of filling:
Xe54 6s2 4f14 5d10 6p2
Short, order of shells:
Xe54 4f14 5d10 6s2 6p2
Four outer shell, valence electrons; group 4A;
once the inner shell d’s and f’s are full: core electrons
Group Work:
Ag, Z= 47 Short: Order of Filling
Short: Order of Shells
Sb, Z= 51 Short: Order of Filling
Short: Order of Shells
Rf, Z= 104 Short: Order of Filling
Short: Order of Shells
Circle valence electrons in short form, order of shells
Key:
Ag, Z= 47
Short, Order of Filling: [Kr36] 5s24d9
Short, Order of Shells: [Kr36] 4d9 5s2
Sb, Z= 51
Short: Order of Filling [Kr36] 5s2 4d10 5p3
Short: Order of Shells [Kr36] 4d10 5s2 5p3
Rf, Z= 104
Short: Order of Filling [Rn86] 7s2 5f14 6d2
Short: Order of Shells [Rn86] 5f14 6d2 7s2
5s14d10
4d10 5s1
Electronic Configuration of Ions
The electronic configurations we have developed
give the basis for the charges we have already
assigned to many elements when they are found as
ions in an ionic type compound.
The main group elements (columns 1A-8A) lose, gain
or share valence electrons in forming compounds so
that they can achieve an outer shell configuration,
when possible, of the nearest noble gas.
When electrons are transferred from one element to
another, charged particles called ions are formed.
We have already assigned a positive charge, equal to
the column number, for ions formed from elements in
columns 1A, 2A and selected 3A elements.
Note how this correlates with configurations we have
done:
Na, Z=11, Column 1A, +1 cation:
2
2
6
1s 2s 2p 3s
1
-1e
+
Na
1s 2s 2p Neon configuration
2
2
6
Column 1A: All Ions, +1
H
Li
Z=1
Z=3
1s
1
H
2
He 2s
1
Li
1+
1+
Nearest noble gas
2
He
Na Z=11
Ne10 3s1
Na 1+
K
Ar18 4s1
K
1+
Ar18
Rb
1+
36
Z=19
36
5s
1
Ne10
Rb Z= 37
Kr
Kr
Cs Z= 55
Xe54 6s1
Cs 1+
Xe54
Fr Z= 87
Rn86 7s1
Fr
1+
Rn86
Since all 1A elements share the same outer shell
configuration, “s1”, they are all expected to form
the same charged ion, +1.
All elements in column 2A, with the outer shell
configuration of “s2” show a + 2 charge, losing both
these electrons to form the noble gas configuration:
Ba, Z=56, Column 2A, +2 cation:
54
2
[Xe ] 6s
- 2e
[Xe54]
Ba 2+
Xenon configuration
Column 2A: All Ions, +2
Be
Z=4
2
He 2s
2
Be
2+
2
He
Ne10 3s2
Mg 2+
Ne10
Ca Z=20 Ar18 4s2
Ca 2+
Ar18
2+
36
Mg Z=12
36
Sr Z= 38 Kr
5s
2
Sr
Kr
Xe54 6s2
Ba 2+
Xe54
Ra Z= 88 Rn86 7s2
Ra 2+
Rn86
Ba Z= 56
In the p block, elements filling the p subshell, both
cations and anions are formed: let’s consider the
cations first...
Aluminum, in group 3A, loses outer s and p
electrons to form a + 3 cation:
Al, Z=13, Column 3A, +3 cation:
2
2
6
2
1
1s 2s 2p 3s 3p
-3e
Al3+
1s2 2s2 2p6 Neon configuration
Other metals in the p block show variable charges,
losing either the p e’s only or the p’s and s’s
P Block metals: Variable Charges
Tl Z=81 Xe544f145d106s26p1 Tl
1+
Xe544f145d106s2
Tl Z=81 Xe544f145d106s26p1 Tl
3+
Xe544f145d10
Pb Z=82 Xe544f145d106s26p2 Pb
2+
Xe544f145d106s2
Pb Z=82 Xe544f145d106s26p2 Pb
4+
Xe544f145d10
Bi Z=83 Xe544f145d106s26p3 Bi
3+
Xe544f145d106s2
Bi Z=83 Xe544f145d106s26p3 Bi
5+
Xe544f145d10
Also: Ga, In: 1+, 3+; Sn, 2+, 4+; lower charges more common
Anions of the P Block
The non-metals in columns 5, 6 and 7 are most likely
to form monoatomic anions; the metalloids of these
groups are less likely to be found as these anions.
In all cases, these elements gain sufficient e’s to
become “isoelectric” with following noble gas.
“ISOELECTRIC”: same number of electrons
Anions Isoelectric with Neon:
N, Z=7, Column 5A, -3 anion:
1s2 2s2 2p3
+3e
N 3-
1s2 2s2 2p6 Neon
configuration
O, Z=8, Column 6A, -2 anion:
2
2
1s 2s 2p
4
+2e
O21s2 2s2 2p6
Neon
configuration
F1-
F, Z=9, Column 7A, -1 anion:
2
2
1s 2s 2p
5
+1e
1s2 2s2 2p6
Neon
configuration
Anions Isoelectric with Argon:
P, Z=15, Column 5A, -3 anion:
2
2
6
2
+3e
3
1s 2s 2p 3s 3p
P31s2 2s2 2p63s2 3p6 Argon
configuration
S, Z=16, Column 6A, -2 anion:
2
2
6
2
4
+2e
1s 2s 2p 3s 3p
S21s2 2s2 2p63s2 3p6 Argon
configuration
Cl, Z=17, Column 7A, -1 anion:
2
2
6
2
5
1s 2s 2p 3s 3p
+1e
Cl11s2 2s2 2p63s2 3p6 Argon
configuration
Let us consider the “variable charge” transition elements:
these metals can utilize both their outer s and their inner d
electrons for ion formation, and they are not as likely to
revert to a noble gas in the process:
In forming ions, the outermost electrons, the “s” e’s, are
lost first to form a +2 ion which most transition elements
exhibit. The other charges arise from subsequent loss
of 1 or more d electrons.
s’s lost first, then d’s
Fe, Z=26 Column 8A, +2 cation:
18
6
[Ar ] 3d 4s
2
-2e
[Ar18] 3d6 Fe2+
Fe, Z=26 Column 8A, +3 cation:
18
6
[Ar ] 3d 4s
2
-3e
[Ar18] 3d5 Fe3+
Note that in the second cation, Fe3+, The 3d subshell
consists of 5 unpaired, same spin electrons, leading
us next to a consideration of the topic of magnetism...
But first: Group Work...
GROUP WORK
Do: Short form, order of shells for atom,
then for ion:
Ag, Ag+
I, I 1-
Zn, Zn 2+
Se, Se2-
Key:
Ag, Z=47: [Kr36] 4d105s1
Ag1+ : [Kr36] 4d10
Zn, Z=30: [Ar18] 3d104s2
Zn 2+: [Ar18] 3d10
I, Z=53: [Kr36] 4d105s25p5
I 1-: [Kr36] 4d105s25p6
Se, Z= 34: [Ar18] 3d104s24p4
Se2- : [Ar18] 3d104s24p6
Magnetism
Substances may be classified under this heading
three ways:
a) diamagnetic: slightly repelled by a strong magnet
b) paramagnetic: attracted to a magnetic field,
c) ferromagnetic: strongly attracted to magnetic field
Most substances fall into the category of
“diamagnetic”, meaning that they appear to be
un-attracted to ordinary “kitchen” magnets, are
are actually slightly repelled by strong magnetic
fields generated in the laboratory.
A significant number of metals and compounds are
attracted to strong magnetic fields in the lab although
they are not attracted to weak magnets of the
“refrigerator” variety: they are “paramagnetic.”
On the other hand, the compounds or metals exhibiting
“ferromagnetism” are used to make up ordinary
household magnets and are attracted to weak and
strong magnetic fields.
Examples of this type are the salt magnetite, Fe3O4, and
“Alnico” an alloy of Al, Ni and Co.
The characteristic which separates compounds and
elements into these categories turns out to be one
that is predicted by electronic configurations: the
presence or absence of unpaired electrons in the
ion or the atom...
Diamagnetism: no unpaired electrons in atom or
either ion of compound;
Paramagnetism: one or more unpaired electron in
atom or either ion of compound;
Ferromagnetism: many unpaired electrons in atom or
either ion of compound.
We find unpaired electrons in the metallic elements when
subshells are unfinished:
Metals in Column 1A,(s1); 3A,(s2p1) 4A (s2p2), 5A,(s2p3)
are predictably paramagnetic, as well as the transition
and inner transition metals, d and f subshell fillers.
Nonmetallic elements, except oxygen, form polyatomic
molecules with no unpaired e’s, all diamagnetic ).
Most compounds have no unpaired electrons and are
diamagnetic as well; they have been lost, gained or
shared in the bonding process. The notable exceptions
are the ions of the d block metals.
Transition elements have many unpaired electrons in
both atoms and ions, and offer best structures for
ferromagnetism:
Magnetite: Fe2O3:
[Ar18] 3d5 Fe3+
Alnico:
Al, 2s2 2p1; p's shown
Co, Z=27, 4s23d6
Ni, Z=28, 4s23d7
Group Work
Do orbital box diagram for last subshell to be filled
for the following elements, then decide which are
•“diamagnetic” (not attracted to a magnet, no
unpaired e’s)
• “paramagnetic” (unpaired e’s, attracted)
Cs, Ca, Cu, C, Kr
Key:
Cs, Ca, Cu
Cs, Z=55: [Xe54] 6s1
paramagnetic
6s1
Ca, Z=20: [Ar18]3s2
diamagnetic
3s2
Cu, Z=29: [Ar18] 3d10 4s1
paramagnetic
4s1
Key:
C, Kr
C, Z=6: [He2] 2s22p2
paramagnetic
2p2
Kr, Z=36: [Kr36]
All e’s paired
diamagnetic