Class 12th d and f block elements power point presentation

It is d and f block elements ppt.

1. 23-1
Prof.Karkande S.P.
d-Block Element
Loknete Dr. Balasaheb Vikhe Patil (Padmabhushan Awardee)
Pravara Rural Education Society’s
Arts, Commerce & Science College, Alkuti,

2. 23-2
Definition of d-block elements
•d-block elements: The elements of periodic
table belonging to group 3 to 12 are known as
d-Block elements. because in these elements
last electron enters in d sub shell or d orbital .
•The d -block elements lie in between s- and
p-block elements in the long form of periodic
table

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Transition Elements
•A transition element is defined as the one
which has incompletely filled d orbitals in its
ground state or in any one of its oxidation
states.
• i.e. A transition element should have partially
filled (n-1) d orbital.

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Figure 23.1The Position of transition elements (d block) and
inner transition elements (f block) in the periodic
table.

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Electron Configurations of
Transition Metals and their Ions
The d-block elements have the general condensed
ground-state configuration [noble gas]ns
2
(n – 1)d
x
where
n = 4 to 7 and x = 1 to 10.
Periods 6 and 7 elements include the f sublevel:
[noble gas]ns
2
(n – 2)f
14
(n – 1)d
x
where n = 6 or 7.
Transition metals form ions through the loss of the ns
electrons before the (n – 1)d electrons.

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Table 23.1 Orbital Occupancy of the Period 4 Transition
Metals
The number of unpaired electrons increases in the first half of the
series and decreases in the second half, when pairing begins.

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Properties of the Transition Metals
All transition metals are metals, whereas main-group
elements in each period change from metal to nonmetal.
Many transition metal compounds are colored and
paramagnetic, whereas most main-group ionic compounds
are colorless and diamagnetic.
The properties of transition metal compounds are
related to the electron configuration of the metal ion.

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Properties of d block elements
ATOMIC & IONIC SIZE
IONIZATION ENTHALPY
 OXIDATION STATES OF d-BLOCK ELEMENTS
 COLORED IONS
CATALYTIC PROPERTIES
 MAGNETIC PROPERTIES
 FORMATION OF COMPLEX COMPOUNDS

9. 23-9
Trends in the Properties of Transition
Metals Atomic And Ionic Size
Across a period the following trends are observed:
Atomic size decreases at first, then remains relatively
constant.
- The d electrons fill inner orbitals, so they shield outer electrons
very efficiently and the 4s electrons are not pulled closer by the
increasing nuclear charge.
Electronegativity and ionization energies also increase
relatively little across the transition metals of a particular
period.

10. 23-10
Trends in the Properties of Transition
Metals Atomic And Ionic Size
•Along the rows nuclear charge increases but
the penultimate d-sub shell has poor shielding
effect so atomic and ionic size remain almost
same .
•The radii of the third (5d) series are virtually
the same as those of the corresponding
members of the second series.

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Figure 23.3Trends in key atomic properties of Period 4
elements.

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Trends in the Properties of
Transition Metals
Within a group the trends also differ from those observed
for main group elements.
Atomic size increases from Period 4 to 5, but not from
Period 5 to 6.
- The extra shrinkage from the increase in nuclear charge (called
the lanthanide contraction) is roughly equal to the normal size
increase due to adding an extra energy level.
- A Period 6 element has 32 more protons than its preceding
Period 5 group member instead of only 18.

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Trends in the Properties of
Transition Metals Electronegativity
Electronegativity increases within a group from Period 4
to 5, then generally remains unchanged from Period 5 to
6. The heavier elements often have high EN values.
Although atomic size increases slightly down the group, nuclear
charge increases much more, leading to higher EN values.
Ionization energy values generally increase down a
transition group, also running counter to the main group
trend.
Density increases dramatically down a group since atomic
volumes change little while atomic masses increase
significiantly.

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Oxidation States of Transition Metals
Most transition metals have multiple oxidation states.
Elements in Groups 8B(8), 8B(9) and 8B(10) exhibit
fewer oxidation states. The higher oxidation state is less
common and never equal to the group number.
- The +2 oxidation state is common because the ns
2
electrons
are readily lost.
The highest oxidation state for elements in Groups 3B(3)
through 7B(7) equals the group number.
- These states are seen when the elements combine with the highly
electronegative oxygen or fluorine.

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Oxidation States of Transition
Metals
•• Transition elements have variable oxidation
states ,due to very small energy difference
between (n-1)d & ns sub-shell electrons from
both the sub-shell take part in bonding
•• The elements which give the greatest number
of oxidation states occur in or near the middle
of the series. Manganese, for example, exhibits
all the oxidation states from +2 to +7.

16. 23-16
Figure 23.5Aqueous oxoanions of transition elements.
Mn
2+
MnO
4
2−
MnO
4
−
+2 +6 +7
The highest oxidation state for
Mn equals its group number.
VO
4
3−
Cr
2
O
7
2−
MnO
4
−
+5 +6 +7
Transition metal ions are
often highly colored.

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Metallic Properties of Transition
Metals
The lower the oxidation state of the transition metal, the
more metallic its behavior.
Ionic bonding is more prevalent for the lower oxidation
states, whereas covalent bonding occurs more
frequently for higher oxidation states.
Metal oxides become less basic (more acidic) as the
oxidation state increases.
A metal atom in a positive oxidation state has a greater
attraction for bonded electrons, and therefore a greater effective
electronegativity, or valence-state electronegativity, than in the
zero oxidation state. This effect increases as its oxidation state
increases.

18. 23-18
Color and Magnetic Behavior
Most main-group ionic compounds are colorless and
diamagnetic because the metal ion has no unpaired
electrons.
Many transition metal ionic compounds are highly
colored and paramagnetic because the metal ion has
one or more unpaired electrons.
Transition metal ions with a d
0
or d
10
configuration are
also colorless and diamagnetic.

19. 23-19
Figure 23.6Colors of representative compounds of the Period 4
transition metals.
titanium(IV) oxidesodium chromate
potassium
ferricyanide
nickel(II) nitrate
hexahydrate
zinc sulfate
heptahydrate
scandium oxidevanadyl sulfate
dihydrate
manganese(II)
chloride
tetrahydrate
cobalt(II)
chloride
hexahydrate
copper(II) sulfate
pentahydrate

20. 23-20
CATALYTIC PROPERTIES
•Vanadium(V) oxide,V2O5 (in Contact Process)
•Finely divided iron (in Haber’s Process)
• Nickel (in Catalytic Hydrogenation)
• Cobalt (Synthesis of gasoline)
• This property is due to
–Presence of unpaired electrons in their incomplete d orbitals.
–Variable oxidation state of transition metals.
–In most cases , provide large surface area with free valancy.

21. 23-21
The Magnetic Properties of Transition
Metal Complexes
Magnetic properties are determined by the number of
unpaired electrons in the d orbitals of the metal ion.
Hund’s rule states that e
-
occupy orbitals of equal energy
one at a time. When all lower energy orbitals are half-
filled:
The number of unpaired e
-
will depend on the relative
sizes of E
pairing
and Δ.
- The next e
-
can enter a half-filled orbital and pair up by
overcoming a repulsive pairing energy, (E
pairing
).
- The next e
-
can enter an empty, higher, energy orbital by
overcoming Δ.

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