Key Properties and Trends of Transition Metals
Transition metals are actually the various chemical elements that have valence electrons. It means electrons that can promote the formation of chemical bonds in two shells instead of just one. Although the term transformation does not have any specific chemical meaning, it is a convenient name for distinguishing the similarity of the atomic structures and the resulting properties of the elements. They occupy the center portions of the periodic table of elements between the groups on the left and the groups on the right. Specifically, groups 3 (IIIb) through 12 (IIb)
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What is a Metallic Character?
According to the metallic character definition, Metallic character refers to the level of the metal's reactivity. Metals tend to lose electrons in chemical reactions, as implied by their low ionization energy. Metal atoms have a low attraction for electrons within the compound, as indicated by their low electronegativity.
Physical properties related to metallic character involve metallic luster, glossy appearance, high density, high electrical conductivity, and high thermal conductivity. Most of the metals with metallic characters are malleable and ductile and can be deformed without breaking. In this case, Zn, Cd, Hg, and Mn are exceptions. The rest of the elements show one or more metallic characters at room temperature. Except for the metals which are exceptions, the remaining of the elements are hard and have low volatility.
Metallic Character Trend
According to the modern periodic table, the metallic character of an element decreases as we move from left to right in the periodic table. This is due to the fact that, while moving from left to right in a period of time, the number of electrons and protons in an atom is expected to increase, which makes the nuclear force stronger, and therefore it becomes more difficult to lose electrons.
Metallic character increases down the group. This kind of metallic character trend happens because the atomic radius increases while moving down the group, which makes it easier to lose electrons.
How to Recognize Elements with Metallic Trends?
Metallic characters are shown by metals, all of which are on the left side of the periodic table.
The only exception is hydrogen, which is a non-metal under normal conditions. Yet hydrogen behaves like metal when it's liquid or solid, but perhaps you should perceive it non-metallic for most purposes.
Metallic elements occur in certain groups or columns of elements, including alkali metals, alkaline earth metals, transition metals (including lanthanide and actinides below the main body of the periodic table), and base metals.
Other metal categories encompass base metals, noble metals, ferrous metals, heavy metals, and precious metals. Metalloids display some metallic character. However, this family of elements also has some non-metallic properties.
What are Transition Metals?
The metals in the periodic table that mostly consist of the d-block transition elements possessing unique and useful properties are known as transition metals. There are a total of 56 transition elements present in the periodic table which are further classified into three main groups-
D-Block Elements or main transition elements
Lanthanides
Actinides
There are incomplete inner electron shells in the case of transition metals which act as the transitional links between the most electropositive and least electropositive between the series of elements. The characterization of the transition metals can be done by the points listed below-
Colored compounds
Multiple Valences
Capability to form stable complex ions
Transition Metals - Metallic Character
Transition metals possess low ionization energies and several vacant orbitals are present in their outermost shell. This is the reason behind their metallic character. Typical metallic properties are exhibited by transition metals because of the formation of metallic bonds between them. The presence of covalent bonds is indicated by the hardness that these metals possess which is because they have unpaired d-electrons. The unpaired electrons which are present in the d-orbitals may overlap leading to the formation of covalent bonds.
The number of covalent bonds present depends on the number of unpaired electrons. If the number of unpaired electrons is high, the covalent bonds will be formed more. This property leads to an increase in the hardness and strength of the metal.
The transition metals including chromium, molybdenum, and tungsten are known to be very hard metals because they have the maximum number of electrons present in their d-orbital while on the other hand metals like mercury, zinc, and cadmium are not at all hard since no unpaired electrons are present in their d-orbitals.
The metallic depends upon the easiness of a metal with which it loses electrons. When we move left to right across the periodic table, there is an increase in the number of protons and electrons which further leads to an increase in nuclear forces on the electrons which makes it difficult for them to lose electrons, therefore the metallic character while moving left to right decreases. As the atomic radius is increased there is an increase in the metallic character as well. Therefore while moving top to bottom, the metallic character of the elements is increased.
Explanation for the Metallic Character of Transition Elements
Transitional elements have a metallic character because they have low ionization energies as well as several empty orbitals in their outer shells. Such a property leads to the formation of metallic bonds in transition metals and hence demonstrates common metallic properties.
These metals are hard, indicating the presence of covalent bonds. This is due to the presence of unpaired d-electrons in transition metals. The d-orbital containing unpaired electrons can sometimes overlap and establish covalent bonds. The higher the number of unpaired electrons present in the transition metals, the greater the number of covalent bonds formed by them.
The chromium (Cr), tungsten (W) and molybdenum (Mo) metals have a maximum number of unpaired d-electrons. These transition metals are therefore exceedingly difficult. On the other hand, zinc (Zn), cadmium (Cd), and mercury ( Hg) are not extremely hard because they do not have unpaired d-electrons.
Metallic character with Alloys
Although the metallic character is mainly related to pure elements, alloys could also have a metallic character. For example, bronze and most copper, magnesium, aluminum, and titanium alloys usually show a high level of metallicity. A few other metallic alloys consist purely of metals, but most often contain metalloids and nonmetals, while retaining the properties of metals.
Example Questions
1. Give some examples of metals that display metallic character
The metals that display with metallic characters are francium, caesium, sodium, copper, silver, iron, gold, aluminum, etc. Caesium and francium are the elements that display the highest metallic character.
2. How does the atomic radius vary in the metallic trends of transition elements?
The atomic radius increases by going down a group, by moving the outer electrons further away from the nucleus. It makes the electron less attracted to the nucleus. As a result, metals become more reactive as we go down the group.
FAQs on Metallic Character of Transition Metals Explained
1. What is meant by the metallic character of transition metals?
The metallic character of transition metals refers to their ability to exhibit typical metallic properties. This is due to their low ionisation energies and the presence of valence electrons in both the outermost 'ns' and inner '(n-1)d' orbitals. These electrons are delocalised and form strong metallic bonds, leading to properties like high conductivity, lustre, and hardness.
2. What are the key properties that define transition elements as metals?
Transition elements are defined as metals because they possess a distinct set of physical and chemical properties. These include:
Being hard, lustrous, and having high tensile strength.
High melting and boiling points (with some exceptions).
Excellent thermal and electrical conductivity.
Malleability (can be beaten into sheets) and ductility (can be drawn into wires).
A tendency to form positive ions (cations) by losing electrons.
The ability to form alloys with other metals.
3. Why do transition metals generally have very high melting and boiling points?
Transition metals have high melting and boiling points due to the presence of strong metallic bonds. This strength arises because both the outer 'ns' electrons and the inner '(n-1)d' electrons participate in intermolecular bonding. A greater number of unpaired d-electrons leads to stronger bonds. Consequently, a large amount of energy, known as the enthalpy of atomisation, is needed to break these bonds, resulting in high melting and boiling points.
4. How does the metallic character of transition elements change across a period?
As we move from left to right across a period in the d-block, the metallic character generally shows a complex trend but tends to decrease slightly. While the number of d-electrons increases, the effective nuclear charge also increases. This pulls the electron cloud closer to the nucleus, making it harder to lose electrons. As a result, properties like hardness increase initially and then decrease towards the end of the series.
5. Why does the metallic character of transition elements increase down a group?
The metallic character increases down a group because of two main factors. First, the atomic size increases as new electron shells are added. This increased distance between the nucleus and the valence electrons weakens the nuclear pull. Second, the screening effect from the inner electrons becomes more pronounced. Both factors make it easier for the atom to lose its outermost electrons, thus increasing its electropositive or metallic nature.
6. How does the number of unpaired d-electrons influence the strength of metallic bonds?
The strength of metallic bonds is directly related to the number of unpaired d-electrons available for bonding. The more unpaired electrons an atom has, the more electrons it can contribute to the 'sea' of delocalised electrons that hold the metal lattice together. This leads to stronger inter-atomic attraction and a higher enthalpy of atomisation. For instance, chromium (Cr) with five unpaired d-electrons has a very strong metallic bond and a high melting point.
7. What makes transition metals particularly good for forming alloys?
Transition metals are excellent for forming alloys because they have very similar atomic sizes. This similarity allows the atoms of one transition metal to easily replace the atoms of another in its crystal lattice, forming a substitutional alloy. This process creates materials with enhanced properties, such as increased hardness or corrosion resistance, like in the case of steel (iron and carbon) or brass (copper and zinc).
8. Why are zinc (Zn), cadmium (Cd), and mercury (Hg) considered exceptions in terms of metallic character?
Zinc, cadmium, and mercury are often considered exceptions because they have a completely filled d-orbital (d¹⁰ configuration) in both their ground state and their common oxidation states. As a result, the d-electrons do not participate in metallic bonding. The bonding only involves the 'ns' electrons, leading to much weaker metallic bonds. This explains their lower melting points, boiling points, and relative softness compared to other transition metals. Mercury is even a liquid at room temperature.
9. How does the metallic character of transition metals compare to that of s-block metals like sodium?
While both are metals, transition metals generally exhibit stronger metallic character than s-block metals in terms of physical properties. S-block metals (like sodium) are soft and have low melting points because they only use their 'ns' electrons for weak metallic bonding. In contrast, transition metals use both 'ns' and '(n-1)d' electrons, creating much stronger bonds, which makes them harder and gives them higher melting points. However, s-block metals are more electropositive, meaning they lose electrons more readily.
10. Are all d-block elements considered transition elements in terms of their properties?
No, not strictly. According to the CBSE/NCERT curriculum, a transition element is defined as an element that has an incompletely filled d-orbital in its ground state or in any one of its common oxidation states. Based on this definition, elements like zinc (Zn), cadmium (Cd), and mercury (Hg) are considered d-block elements but not typical transition elements because their d-orbitals are completely filled (d¹⁰). This is why their chemical and physical properties often differ from the rest of the transition series.
