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Transition Metals
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Transition Metals

Feb 23, 2016

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Transition Metals. d -Block Elements. Between groups 2 and 3 in the periodic table are found the d -block elements . You may recall that in d -block elements, electrons are being added to the d subshell of the third and subsequent shells. - PowerPoint PPT Presentation
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Page 1: Transition Metals

Transition Metals

Page 2: Transition Metals

d-Block Elements•Between groups 2 and 3 in the periodic

table are found the d-block elements.•You may recall that in d-block elements,

electrons are being added to the d subshell of the third and subsequent shells.

•The first row of d-block elements consists of those elements whose highest energy electrons are filling the 3d subshell.

Page 3: Transition Metals

d-Block Elements•These elements are scandium, titanium,

vanadium, chromium, manganese, iron, cobalt, nickel, copper and zinc.

•Of these, the elements from titanium to copper are considered to be transition elements.▫This distinction is due to the definition of a

transition element as a d-block element that can form at least one stable ion with a partially filled d subshell.

Page 4: Transition Metals

d-Block Elements•If we consider the electron configuration

of these d-block elements and the ions that they can form, we can see clearly why scandium and zinc are not included as transition metals.

Page 5: Transition Metals

d-Block Elements

Page 6: Transition Metals

d-Block Elements•In the case of scandium and zinc, only one

ion exists and that ion does not have a partially filled d subshell.▫The scandium(III) ion, Sc3+, is the only

stable ion of scandium ad has no electrons in the 3d subshell.

▫The zinc(II), Zn2+, ion is the only stable ion of zinc to exist and this ion has a full 3d subshell.

Page 7: Transition Metals

Transition Elements •Properties of transition elements:

▫Their ions can exist in variable oxidation states.

▫They have higher melting points and are harder and denser than group 1 and 2 metals.

▫A number of the elements and their compounds have catalytic properties.

▫They can form complex ions.▫The majority of their complexes are

coloured.

Page 8: Transition Metals

Variable Oxidation States•Transition elements can form ions

with a variety of oxidation states (oxidation numbers).

•All transition elements can form ions with an oxidation of +2, and, in addition, each element can form a number of ions with other oxidation numbers.

Page 9: Transition Metals

Variable Oxidation States•From titanium to manganese, the

maximum oxidation number possible is equal to the total number of 4s and 3d electrons.

•For example, the maximum oxidation number possible for titanium ([Ar]3d24s2) is +4 and for manganese ([Ar]3d54s2) it is +7.

Page 10: Transition Metals

Variable Oxidation States

Page 11: Transition Metals

Variable Oxidation States•The transition elements form ions by

losing electrons from both the 4s and the 3d subshells.

•This is possible because these subshells are very close to each other in energy.

Page 12: Transition Metals

Variable Oxidation States•The variation in oxidation states is easily

recognizable in many transition elements by a change in colour in the new compound.

Page 13: Transition Metals

Physical Properties•The d-block elements are all metals.•They have physical properties that are

typical of metals.▫With the exception of mercury (liquid at

room temperature), their melting points are high and they are solids under standard conditions.

▫They are good conductors of electricity and heat.

▫They are hard, strong and shiny.

Page 14: Transition Metals

Physical Properties•The chemical reactivity of the d-block

elements is relatively low and, together with these physical properties, makes d-block elements extremely useful.

•Iron is used widely for construction of bridges, buildings, vehicles and other structures that require great strength.

•Copper is most valuable for its excellent conduction of electricity and as unreactive, yet malleable, metal for pipes.

Page 15: Transition Metals

Catalytic Properties•A catalyst increases the rate of a

chemical reaction by providing an alternative reaction pathway with a lower activation energy.

Page 16: Transition Metals

Catalytic Properties•The catalyst itself is not consumed.•As the activation energy is lowered,

there will be a greater proportion of particles present at a given temperature with sufficient kinetic energy to overcome the activation energy.

Page 17: Transition Metals

Catalytic Properties• Many transition metals and their compounds

show catalytic activity and they are widely used in industry (where it is desirable to generate maximum quantities of product as quickly as possible to maximize profits).

Page 18: Transition Metals

Catalytic Properties•Solid catalysts have a high surface energy

(the amount of energy required to create a new surface).

•Due to their high surface energies, solid catalysts are able to form strong bonds with the molecules that come into contact with them.

Page 19: Transition Metals

Catalytic Properties•This attraction at the surface of the

catalyst weakens the bonds within the reactant molecules, making it easier to break them apart.

•Collisions with other molecules are now more likely to overcome the activation energy for the reaction, and so the rate of the product formation is increased.

Page 20: Transition Metals

Catalytic Properties• Nickel is used as a catalyst in the hydrogenation

of alkenes to form alkanes.• A practical application of this process is in the

manufacture of margarine.• The vegetable oils used for making margarines

are refined as liquids that are high in unsaturated fatty acids.

• To increase the melting point of the mixture, the fatty acids undergo hydrogenation during which some carbon-carbon double bonds are converted to single bonds and hydrogen is added.

Page 21: Transition Metals

Catalytic Properties•Platinum, rhodium and palladium are

particularly effective industrial catalysts.•Alloys of platinum and rhodium are used

in the catalytic converters of car exhaust systems, where toxic gaseous emissions such as CO, NO and NO2 are broken down into harmless compounds.

Page 22: Transition Metals
Page 23: Transition Metals

Catalytic Properties•Biological catalysts are better known as

enzymes.•Hydrogen peroxide is a toxin in the

human body.•Its decomposition is catalyzed by the

enzyme catalase.•In the lab the decomposition of hydrogen

peroxide can be catalyzed by a number of inorganic catalysts, such as MnO2.