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8afc25342b78534
8.2 Periodic Classification of the Elements
 8.3 Periodic Variation in Physical Properties
 Effective nuclear charge
 Atomic Radius
 Ionic Radius
 8.4 Ionization Energy
 8.5 Electron Affinity
 Electronegativity (ch.9 p. 377-378)

p357: 8.5, 8.8, 8.12, 8.20, 8.24, 8.26, 8.28, 8.30, 8.32
p358: 8.36, 8.38, 8.40, 8.44, 8.46
p358: 8.52, 8.54, 8.62, 8.64
Dr.Laila Al-Harbi
Chapter 8 :Classification of elements
☼ Metals – metalloids – non metals in periodic table
1-Representative elements (main group elements):
 Groups 1A to 7A
 Incompletely filled s and p orbitals
 1A = alkaline metals
 2A = alkaline earth metals
 7A = halogens
2-Noble gas group:
 Group 8A
 Filled p subshell (except He which has a filled s orbital)
3-Transition metal
 Groups 1 B to 8 B
 Unfilled d orbitals
4-Lanthanides and actinides
 Incompletely filled f subshells
 Lanthanides = rare earth metals
2
Chapter 8 :Block system of periodic table
ns
ns np
S block
p block
ns (n-1)d
ns
d block
f block
3
The elements in group 4A :carbon (C) is a nonmetal,
silicon (Si)and germanium (Ge)are metalloids, and tin(Sn)
and lead(Pb) are metals .
halogens(nonmetals)(Florine(F),Iodine(I),Chlorine(Cl),Bromi
ne(Br)) form an ion with a charge of (-1)(F-,I-,Cl-,Br-)
Dr.Laila Al-Harbi
d10
d5
d1
Within a group (n) increase
4f
5f
Dr.Laila Al-Harbi
ns2np6
ns2np5
ns2np4
ns2np3
ns2np2
Within a Period number of electrons increase
ns2np1
ns2
ns1
Ground State Electron Configurations of the Elements
Chapter 8 : Classification of the Elements
Valence electrons the outermost electrons
Core electrons are nonvalence electrons in an atom
Example
Na
10 core electrons
1 outermost (valence electron)
Cl
10 core electrons
7 outermost (valence electron)
6
1H
1s1
2He
1s2
3Li
1s22s1
4Be
1s22s2
5B
1s22s22p1
6C
1s22s22p2
7N
8O
9F
10Ne
period 1
1s22s22p3
1s22s22p4
1s22s22p5
1s22s22p6
Period 2
period 2
11Na
1s22s22p63s1
12Mg
1s22s22p63s2
13Al
1s22s22p63s23p1
14Si
1s22s22p63s23p2
15P
1s22s22p63s23p3
16S
1s22s22p63s23p4
17Cl
1s22s22p63s23p5
18Ar
1s22s22p63s23p6
Period 3
Dr.Laila Al-Harbi
19K
1s22s22p63s23p64s1
20Ca
1s22s22p63s23p64s2
21Sc
1s22s22p63s23p64s23d1
22Ti
1s22s22p63s23p64s23d2
23V
1s22s22p63s23p64s23d3
24Cr
1s22s22p63s23p64s13d5
NOT 4s23d4
There is a tendency toward half-filled and
completely filled d subshells. This is a consequence
of the closeness of the 3d and the 4s orbital energies.
Dr.Laila Al-Harbi
The 3d level becomes more stable as
30Zn
we move from left to right on the
periodic chart. Remember there is an 31Ga
increase in the number of protons
consequently, an increase in the
32Ge
number of electrons as we move from
left to right on the chart.
33As
25Mn
26Fe
27Co
1s22s22p63s23p64s23d5
1s22s22p63s23p64s23d6
1s22s22p63s23p64s23d7
28Ni
1s22s22p63s23p64s23d8
29Cu
1s22s22p63s23p64s13d10
34Se
1s22s22p63s23p64s23d10
1s22s22p63s23p64s23d104p1
1s2 2s22p63s23p64s23d104p2
1s2 2s22p63s23p64s23d104p3
1s22s22p63s23p64s23d104p4
35Br
1s22s22p63s23p64s23d104p5
36Kr
1s22s22p63s23p64s23d104p6
NOT 4s23d9
Additional exceptions are Mo 5s14d5;
Ag 5s14d10; Au 6s15d10
That is reasonable considering their position on the periodic chart.
Dr.Laila Al-Harbi
The general formula of
an element un group IA
is
A. S2
B. S1
C. S2p1
D. s1p1

The general formula of
an element un group
8A is
A. S2
B. S1
C. S2p6
D. s1p1

Dr.Laila Al-Harbi
Electron Configurations of Cations and Anions
Of Representative Elements
Na [Ne]3s1
Na+ [Ne]
Ca [Ar]4s2
Ca2+ [Ar]
Al [Ne]3s23p1
Al3+ [Ne]
Atoms gain electrons so that
anion has a noble-gas outer
electron configuration.
Atoms lose electrons so that
cation has a noble-gas outer
electron configuration.
H 1s1
H- 1s2 or [He]
F 1s22s22p5
F- 1s22s22p6 or [Ne]
O 1s22s22p4
O2- 1s22s22p6 or [Ne]
N 1s22s22p3
N3- 1s22s22p6 or [Ne]
Dr.Laila Al-Harbi
Dr.Laila Al-Harbi
-1
-2
-3
+3
+2
+1
Cations and Anions Of Representative Elements
Na+: [Ne]
Al3+: [Ne]
O2-: 1s22s22p6 or [Ne]
F-: 1s22s22p6 or [Ne]
N3-: 1s22s22p6 or [Ne]
Na+, Al3+, F-, O2-, and N3- are all isoelectronic with Ne
What neutral atom is isoelectronic with H- ?
H-: 1s2
same electron configuration as He
isoelectronic – same number of electrons
10Na+, 10Al3+, 10F-, 10O2-,
11Na , 13Al
and 10N3-
, 9F , 8O , and 7N
Dr.Laila Al-Harbi
Electron Configurations of Cations of Transition Metals
When a cation is formed from an atom of a transition metal,
electrons are always removed first from the ns orbital and then from
the (n – 1)d orbitals.
Fe:
[Ar]4s23d6
Fe2+: [Ar]4s03d6 or [Ar]3d6
Mn:
[Ar]4s23d5
Mn2+: [Ar]4s03d5 or [Ar]3d5
Fe3+: [Ar]4s03d5 or [Ar]3d5
keep in mid that most transition metals an form more than
one cation and frequently the cations are not isoeletronic
with the preceding noble gases
Dr.Laila Al-Harbi










What is the ground-state
electron configuration of
Mn?
3d5
4s1 3d5
4s2 3d6
4s2 3d5
What is the ground-state
electron configuration of
Mn+2
3d5
4s1 3d5
4s2 3d6
4s2 3d5










What is the ground-state
electron configuration of
Fe+2
3d6
4s1 3d5
4s2 3d6
4s2 3d5
What is the ground-state
electron configuration of
Fe+3
3d5
4s1 3d5
4s2 3d6
4s2 3d5
Dr.Laila Al-Harbi
Gallium element is found in the periodic
table in
(a) period 3, group 1B
(b) period 3A, group 4
(c) period 4, group 1A
(d) period 4, group 3A
Answer (d)
Dr.Laila Al-Harbi
Titanium (Ti) element is found in the periodic
table in
(a) s-block
(b) P-block
(c) d-block
(d) f-block
The 15th element
in the period 4 is
(a) s-block
(b) P-block
(c) d-block
(d) f-block
Dr.Laila Al-Harbi
Which of the following species is isoelectronic
with Cl(a) F(b) O2(c) K+
(d) Na+

Answer: (c)
Dr.Laila Al-Harbi
14
7
1.




19
9
F
2.
20
10
3.
19
9
4.
14
7

Ne
F
20
10
5.


19
9
20
10
F
24
12
Ne
Ne
24
12
Mg

20
10 Ne
3
N

N 3
20
10
Ne

27
3
Al
13
27
13
None of the above


Al 3




Mg
27
13
Al 3
An atom of a certain element has 15 electrons.
Without consulting a periodic table, answer
the following questions:
(a) What is the ground-state electron
configuration of this element?
1s2 2s2 2p6 3s2 3p3 Valence electrons
(b) How should be element be classified?
Period 3, group 5A
The element is representative
element.
(c) Is the element diamagnetic or paramagnetic
paramagnetic

3s2
3p3
Periodic Variation in Physical Properties
Effective nuclear charge ‫شحنه النواه الفعالة‬
Atomic Radius ‫نصف القطر الذري‬
Ionic Radius ‫نصف القطر االيوني‬
Ionization Energy ‫طاقة التأين‬
Electron Affinity ‫األلفة االلكترونية‬
Electronegativity ‫السالبية الكهربية‬
Effective nuclear charge
 Atomic Radius
 Ionic Radius

‫ هي الشحنة الموجبة التي‬:‫الشحنة النووية الفعالة‬
‫تشعر بها االلكترونات الموجودة في تلك الذرة‬
.‫وخاصة في المستوى األخير للذرة‬
Effective nuclear charge
 lower effective charge on nucleus
• inner electrons shield outer electrons from nucleus
• shielding effect of electrons reduces the attraction between the
nucleus and the electrons
• repulsive forces between electrons offset the attractive forces


Dr.Laila Al-Harbi
Effective nuclear charge (Zeff) is the “positive charge” felt by an
electron.
Zeff = Z - s
0 < s< Z (s = shielding constant)
Zeff  Z – number of inner or core electrons
Z
Core
Zeff
Radius
Na
11
10
1
186
Mg
12
10
2
160
Al
13
10
3
143
Si
14
10
4
132
Within a Period
as Zeff increases
radius decreases
decreases
Dr.Laila Al-Harbi
Decreasing Zeff
Increasing n increases the shielding effect
Increasing Zeff
increasing Z (nuclear charge)

The atomic radius is ½ the distance between the 2 nuclei
of the adjacent atoms.

Atomic radius - a number of physical properties of
elements are related to the size of an atom

Atomic radius, in general, decreases as we move from
left to right in a row of the periodic table (a Period ).

Atomic radius increases from top to bottom in a family
or group.

The ionic radius is the radius of anions and Cations
Dr.Laila Al-Harbi
Dr.Laila Al-Harbi
Increasing atomic radius
n increases so atomic radius increases
Decreasing atomic radius
increasing Z increases the effective nuclear charge so the added valence electron
is more strongly attracted by the nucleus so atom size shrinks
Within a group atomic radius increase
Within a Period atomic radius decreases
Dr.Laila Al-Harbi

Referring to a periodic table, arrange the
following atoms in order of increasing atomic
radius: P , Si , N
increasing … small to large
( small) N < P < Si (large)

arrange the following atoms in order of decreasing radius:
C , Li, Be
 decreasing
… large to small
(large) Li > Be > C (small)
Dr.Laila Al-Harbi

Anions>>gain electrons >>> ionic radius increase because the
nuclear charge remain the same but the repulsion resulting from the
additional electrons enlarges the domain of the electron

Cations… lose electron …ionic radius decrease because removing
one or more electron from an atom reduces electron-electron
repulsion but the nuclear charge remains the same so the electron
clouds shrinks , and the cation is smaller than atom
Cation is always smaller than atom from which it is formed.
Anion is always larger than atom from which it is formed.
Dr.Laila Al-Harbi
Atom
ionic radius
decrease
Anion
Cation
Atom
Dr.Laila Al-Harbi
ionic
radius
increase







Isoelectronic ions
Cations is smaller than anions ( 10Na+<
The greater effective nuclear charge of
10Na+results in smaller radius.
Isoelectronic cations
10Al+3< 10Mg+2 < 10Na+
Isoelectronic anions
10F- < 10O-2 < 10N-3
Dr.Laila Al-Harbi
10F-)
Dr.Laila Al-Harbi
ionic radius increase




For each of the following
pair ,indicate which is
larger
A) 10F- ,10N-3
10N-3
B) 10Mg+2 , 18Ca+2
18Ca+2
C) Fe+2 , Fe+3
Fe+2


For each of the
following pair ,indicate
which is smaller
A) 18K+ ,2Li+
2 Li+

B)
10N-3
,
18P-3

C) Au+ , Au+3
10N-3
Au+3
Dr.Laila Al-Harbi
‫‪Order the following according to increasing atomic/ionic‬‬
‫‪radius.‬‬
‫–‪N3– Li+ C O2‬‬
‫–‪C < Li+ < O2– < N3‬‬
‫‪N3– < O2– < C < Li+‬‬
‫–‪Li+ < C < N3– < O2‬‬
‫–‪Li+ < C < N3– < O2‬‬
‫–‪Li+ < C < O2– < N3‬‬
‫ايونات من مجموعات مختلفه؟‬
‫الكاتيونات اصغر من االنيونات‬
‫كاتيونات‪ :‬االصغر ذو الشحنه الموجبه االكبر‬
‫انيونات ‪ :‬االصغر ذو الشحنه السالبه االصغر‬
‫‪1.‬‬
‫‪2.‬‬
‫‪3.‬‬
‫‪4.‬‬
‫‪5.‬‬



Ionization energy (IE) is the minimum energy (kJ/mol)
required to remove an electron from a gaseous atom in its
ground state.
The higher ionization energy, the more difficult it is to remove
the electrons.
The first ionization energy is the amount of energy required
to remove the 1st electron from an atom in the gaseous state.
I1 + X
I2 + X
I3 + X
(g)
X+(g) + e-
I1 first ionization energy
(g)
X2+(g) + e-
I2 second ionization energy
(g)
X3+(g) + e-
I3 third ionization energy
I1 < I2 < I3
Dr.Laila Al-Harbi
The higher ionization energy,
the more difficult is to remove
the electrons.
Variation of the First Ionization Energy with Atomic Number
A larger effective nuclear charge
more tightly held outer
electron,
higher first ionization energy.
He has the highest first ionization energy of all the elements.
Filled n=1 shell
Filled n=2 shell
Filled n=3 shell
Filled n=4 shell
Filled n=5 shell
Decreasing First IE I1
n increases so the Zeff decreases and easier
to remove electrons
Increasing First IE (I1)
increasing Z increases the effective nuclear charge so the added valence electron
is more strongly attracted by the nucleus and harder to remove electrons

When electron is removed from atom, repulsion among the remaining
electrons decrease, because nuclear charge remains constant. More energy
is needed to remove another electron from the positively charged ion.

The IE for nonmetal is higher than metal , IE for metalloid fall between
metals and nonmetals.

The first IE increase from left to right in period.
But there is some exceptions

A)
Group 2A (ns2 ) higher than 3A (ns2 np1) in the same period
Example (Be & B)
B) Group 5A (ns2 np3) higher than 6A (ns2 np4) in the same period
Example (N & O)
Some irregularities (Exceptions) of Ionization Energy
1A < 3A < 2A < 4A < 6A < 5A < 7A < 8A √
Decreasing First Ionization Energy
Increasing First Ionization Energy
Example 8.4 (a) p340:
Solution:
O & S are in group 6A
O: [He] 2s2 2p4
S: [Ne] 3s2 3p4
Decreasing First Ionization
Energy
Which atom should have a
smaller first ionization energy:
oxygen or sulphur?
The valence electrons in
sulphur are farther ‫ ابعد‬from the
nucleus → removing of them is
easier
Thus: I1 (S) < I1 (O)
Increasing First Ionization Energy
Which atom should have a
higher second ionization
energy (Li or Be)

Li (2s1) < Be (2s2 ) … first

Li+ (1s2) > Be+ (2s1 ) …

ionization energy
second ionization energy
Because 1s electrons
shield 2s electrons much
more effectively than they
shield each other , we
predict that it should be
easier to remove a 2s
electron from Be+ than to
remove a 1s electron from
Li+
Decreasing First Ionization
Energy

Increasing First Ionization Energy
‫هي كمية الطاقة الممتصة عند إضافة إلكترون لذرة‬
.1- ‫غازية متعادلة لتكوين أيون غازي بشحنة مقدارها‬
.‫وتصبح شحنتها سالبة عند انطالق الطاقة‬

F
Electron affinity is the negative of the energy
change that occurs when an electron is
accepted by an atom in the gaseous state to
form an anion.
+ e-
X
(g)
(g)
+ e-
O
(g)
+ e-
X-(g)
X-(g)
DH = -328 kJ/mol
EA = +328 kJ/mol
O-(g)
DH = -141 kJ/mol
EA = +141 kJ/mol
The higher electron affinity, the greater affinity to accept the electron
Dr.Laila Al-Harbi
Decreasing Electron affinity
n increases so the Zeff decreases and less
electron acceptance
Increasing Electron affinity
increasing Z increases the effective nuclear charge so the more electron
acceptance and greater electron affinity
Highest Electron affinity is for halogen
Lowest Electron affinity is for group IA
Dr.Laila Al-Harbi

The EA for nonmetal is higher than metal , EA for metalloid fall
between metals and nonmetals.

The EA increase from left to right in period.

But there is some exceptions
A) Group 2A (ns2 ) lower than 1A (ns1 ) in the same period
B) Group 5A (ns2 np3) lower than 4A (ns2 np2) in the same period
◦
Noble gases have the lowest electron affinities
◦
The electron affinity of (F) is lower than that for the (Cl)
◦
8A < 2A < 1A < 3A < 5A < 4A < 6A < 7A
Chapter 8 : Electron Affinity
>
>
Q: Which choice correctly lists the elements in
order of decreasing electron affinity?
‫من األكبر إلى األصغر‬
b.
c.
d.
O, Cl, B, C
O, Cl, C, B
Cl, O, C, B
Cl, O, B, C
1. Exceptions?? No
2. Apply the rule of the
period until you find
a group apply the
rule of the group
Increasing Electron affinity
Decreasing Electron affinity
a.
Cl > O > C >B

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