Transition metals are hard...!! Give reasons.
Answers
Answered by
3
A transition metal or element is generally defined as a metal which has partially filled d orbitals in the neutral atom or in any of its usual positive oxidation states.
The first transition series extends from scandium (Sc) to copper (Cu).
Electronic Configuration of The First Transition Series
21Sc - [Ar] 3d14s2
22 Ti - [Ar] 3d24s2
23V - [Ar] 3d3s2
24Cr - [Ar] 3d54s1
25Mn - [Ar] 3d54s2
26Fe - [Ar] 3d64s2
27Co - [Ar] 3d74s2
28Ni - [Ar] 3d84s2
29Cu - [Ar] 3d104s1
Note:
*[Ar] represents the electronic configuration of argon (1s22s22p63s23p6), which comes before the outer electronic levels of transition elements.
Only the outer electronic configuration are shown above. However, always write the complete configurations whenever you are asked to write the electronic configurations of transition metals, example, Sc 1s22s22p63s23p63d14s2.
*All the elements have their d orbitals partially filled. Example, 27Co - 3d74s2 and 28Ni3d84s2 .
Zinc has completely filled d orbitals, it is therefore not regarded as a transition metal.
*The electronic configuration of chromium is predominantly [Ar] 3d54s1 instead of [Ar] 3d44s2 as you might have expected.
The reason why this is the case is that, having five electrons in the d orbitals produces a kind of stability known as partial stability on the metal, considering that five is half of ten (for full stability).
Therefore, after vanadium, the next electron, together with one electron of 4s preferably go into d orbitals (to make it five). The same reason explains the configuration of copper as shown above.
Properties (Physical and Chemical) of Transition Elements
Transition metals show unique physical and chemical properties. These include:
Physical Properties
1. They are all Metals.
2. They are hard, malleable, ductile and are of very high melting and boiling points. Compared with the main group metals (such as metals of group one), transition metals have higher boiling and melting point .
The reason for this is the presence of very strong metallic bonding - due to large number of valence electrons involved in it.
3. They are good conductors of electricity. This is because their electrons are very free to move about within the available vacant d orbitals.
4. They exhibit paramagnetism. This is due to the presence of unpaired electrons.
Paramagnetism is the phenomenon whereby substances are weakly attracted into a magnetic field. Substances which are paramagnetic contain one or more electrons that are not paired off in the usual way.
Consequently, there is a magnetic moment which results in attraction by a magnetic field. The higher the number of unpaired electrons, the greater the paramagnetic properties.
Example, 27Co has three unpaired electrons as shown above, and is therefore more paramagnetic than 28Ni, which has two.
Note that a diamagnetic substance is repelled by a magnetic field. All its electrons are paired.
Complex ion Formation
Transition metal ions have small cationic size, large ionic charge and empty or partially filled 3d orbitals, hence they are capable of accepting electron pairs from either charged or neutral particles into their d orbitals to form dative or coordinates bonds, resulting in complex ion formation.
The electron donors are called ligands (examples, NH3, H2O, and CN-, and ethylene diamine NH2CH2CH2NH2). The number of ligands attached to a metal ion is regarded as its coordination number and it is commonly 4 to 6.
Complex ion formation are aided by the following factors:
(a). Oxidation number - complex ion formation increases with increase in oxidation number. That is, the higher the oxidation number of the element, the greater the stability of the complex ion formed.
Example, hexamine cobalt(III) ion, [Co(NH3)6]3+ is more stable than hexamine cobalt(II) ion, [Co(NH3)6]2+ as it does not lose ammonia, while the cobalt(II) loses ammonia and gives the reaction of cobalt(II) in solution.
(b). Atomic number - the stability of a particular complex ion increases within a transition series with increase in atomic number. Example, the stability of complex ion formed between NH3 and a transition metal in the oxidation state of +2, from Mn to Cu is in the order:
Cu2+> Ni2+ > Co2+ > Fe2+
(c). The nature of ligands
The stability of complex ion formed also depends on the degree of interaction between the ligand and the central ion.
Some ligands form more stable complexes than others. Example, the following is the order of stability of certain ligands with the same transition metal ion (in the same oxidation state):
Cu(CN)42- > Cu(NH3)42+ > Cu(H2O)42+
3. Formation of coloured ions - transition metal ions tend to be highly coloured. This is due to the easy movement of electrons between the d orbitals, resulting in absorption or emission of light whose frequencies lie in the visible region.
The first transition series extends from scandium (Sc) to copper (Cu).
Electronic Configuration of The First Transition Series
21Sc - [Ar] 3d14s2
22 Ti - [Ar] 3d24s2
23V - [Ar] 3d3s2
24Cr - [Ar] 3d54s1
25Mn - [Ar] 3d54s2
26Fe - [Ar] 3d64s2
27Co - [Ar] 3d74s2
28Ni - [Ar] 3d84s2
29Cu - [Ar] 3d104s1
Note:
*[Ar] represents the electronic configuration of argon (1s22s22p63s23p6), which comes before the outer electronic levels of transition elements.
Only the outer electronic configuration are shown above. However, always write the complete configurations whenever you are asked to write the electronic configurations of transition metals, example, Sc 1s22s22p63s23p63d14s2.
*All the elements have their d orbitals partially filled. Example, 27Co - 3d74s2 and 28Ni3d84s2 .
Zinc has completely filled d orbitals, it is therefore not regarded as a transition metal.
*The electronic configuration of chromium is predominantly [Ar] 3d54s1 instead of [Ar] 3d44s2 as you might have expected.
The reason why this is the case is that, having five electrons in the d orbitals produces a kind of stability known as partial stability on the metal, considering that five is half of ten (for full stability).
Therefore, after vanadium, the next electron, together with one electron of 4s preferably go into d orbitals (to make it five). The same reason explains the configuration of copper as shown above.
Properties (Physical and Chemical) of Transition Elements
Transition metals show unique physical and chemical properties. These include:
Physical Properties
1. They are all Metals.
2. They are hard, malleable, ductile and are of very high melting and boiling points. Compared with the main group metals (such as metals of group one), transition metals have higher boiling and melting point .
The reason for this is the presence of very strong metallic bonding - due to large number of valence electrons involved in it.
3. They are good conductors of electricity. This is because their electrons are very free to move about within the available vacant d orbitals.
4. They exhibit paramagnetism. This is due to the presence of unpaired electrons.
Paramagnetism is the phenomenon whereby substances are weakly attracted into a magnetic field. Substances which are paramagnetic contain one or more electrons that are not paired off in the usual way.
Consequently, there is a magnetic moment which results in attraction by a magnetic field. The higher the number of unpaired electrons, the greater the paramagnetic properties.
Example, 27Co has three unpaired electrons as shown above, and is therefore more paramagnetic than 28Ni, which has two.
Note that a diamagnetic substance is repelled by a magnetic field. All its electrons are paired.
Complex ion Formation
Transition metal ions have small cationic size, large ionic charge and empty or partially filled 3d orbitals, hence they are capable of accepting electron pairs from either charged or neutral particles into their d orbitals to form dative or coordinates bonds, resulting in complex ion formation.
The electron donors are called ligands (examples, NH3, H2O, and CN-, and ethylene diamine NH2CH2CH2NH2). The number of ligands attached to a metal ion is regarded as its coordination number and it is commonly 4 to 6.
Complex ion formation are aided by the following factors:
(a). Oxidation number - complex ion formation increases with increase in oxidation number. That is, the higher the oxidation number of the element, the greater the stability of the complex ion formed.
Example, hexamine cobalt(III) ion, [Co(NH3)6]3+ is more stable than hexamine cobalt(II) ion, [Co(NH3)6]2+ as it does not lose ammonia, while the cobalt(II) loses ammonia and gives the reaction of cobalt(II) in solution.
(b). Atomic number - the stability of a particular complex ion increases within a transition series with increase in atomic number. Example, the stability of complex ion formed between NH3 and a transition metal in the oxidation state of +2, from Mn to Cu is in the order:
Cu2+> Ni2+ > Co2+ > Fe2+
(c). The nature of ligands
The stability of complex ion formed also depends on the degree of interaction between the ligand and the central ion.
Some ligands form more stable complexes than others. Example, the following is the order of stability of certain ligands with the same transition metal ion (in the same oxidation state):
Cu(CN)42- > Cu(NH3)42+ > Cu(H2O)42+
3. Formation of coloured ions - transition metal ions tend to be highly coloured. This is due to the easy movement of electrons between the d orbitals, resulting in absorption or emission of light whose frequencies lie in the visible region.
Answered by
0
Presence Of Covalent Bond
Explanation:
- The presence of covalent bonds is the reason for hardness of transition metal
- Transition metals have unpaired d-electrons that results in the formation of covalent bonds
- The d-orbital having the unpaired electrons overlap with each other to form covalent bonds
- The unpaired electrons present in d-sub shell can be easily de-localized and gets participated in the bonding of metal
∴ These transition metals are very strong and hard and have high melting point.
Similar questions