Physical Properties of Group IIIB ElementsHomework Help, Tutoring
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Physical Properties of Group IIIB Elements
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Physical Properties of Group IIIB Elements
Group III B includes boron, aluminum, gallium, indium and thallium. All the members of group IIIB
contain three electrons in the outermost orbit. Hence, they have an outer electronic configuration
of ns2np1. As the outer most electrons are present in the p-shell they are included in the P-block.
Here is a list of physical properties by these elements.
Physical properties:
Atomic and ionic radius: atomic radius increases from boron to thallium. From boron to aluminum, the
atomic radius increases greatly. This increase is due to greater screening effect caused by the eight
electrons present in the penultimate shell. This is not seen in case of boron as it has only two electrons
in the penultimate shell. In case of ionic radius, it increases from boron to thallium.
Density:
Density increases from B to TI. This is due to increase in the size of the atom. Of all the elements, aluminum
is of very low density and is widely used as a structural material.
Melting and boiling points:
Melting point decreases from B to Ga and then it gradually increases. Boron has a very high melting point due to its existence
as a giant covalent polymer in both solid and liquid states. Gallium has a very low melting point and remains as liquid up to
2000ο.
Ionization energy:
Though the members of p-block have large nuclear charge and small size, the first ionization energies of these elements
are less than the corresponding values of s-block elements. The electrons are far away from the nucleus and are held less
tightly. Hence, they can be removed very easily. However, the average of the first three ionization energies is very high
and decrease as we move down the group.
Electropositive character:
Electropositive nature increases from B to TI. Boron acts as a semi-metal while all the other elements show metallic nature.
Oxidation states:
As there are three electrons in the outermost orbit, they show oxidation states of +1 and +3. Boron exhibits only the
+3 oxidation state and all the other elements show both the oxidation states. The stability of +1 oxidation state
increases as we move down the group. Thus, thallium which shows a +1 oxidation state is highly stable. This is due
to the inert pair effect. (Inert pair effect means the two s-electrons in the outer shell remain paired and do not
participate in compound formation).
Ability to form ionic compounds:
The tendency to form ionic compounds increases as we move down the group. Boron forms only covalent compounds.
This is mainly due to its high ionization energy and small size. The small size of boron enables it to exert
strong polarizing effect on neighboring atoms and pulls off the electrons from neighboring atoms. As the ionic
size increases as we move down the group, the tendency to form covalent bond decreases.
Oxidation potential or reducing property: the oxidation potentials of the elements of group III B are very high. This is due to high heat of hydration which is due to high charge and small radius of trivalent ions M3+. Aluminum is a very strong reducing agent.
Complex formation: the smaller size and greater charge of group IIIB elements enable them to have a greater tendency to form complexes than the s-block elements.
Oxidation potential or reducing property: the oxidation potentials of the elements of group III B are very high. This is due to high heat of hydration which is due to high charge and small radius of trivalent ions M3+. Aluminum is a very strong reducing agent.
Complex formation: the smaller size and greater charge of group IIIB elements enable them to have a greater tendency to form complexes than the s-block elements.
Solved problems
- Which of the following have a greater tendency to form complexes?
- P-block elements
- S-block elements
- Both
- Both do not form complexes
- Which of the following elements can only form covalent compounds
- Boron
- Aluminum
- Gallium
- Indium
- The high stability of +1 oxidation state of thallium is due to
- Small size
- Inert pair effect
- Larger atomic radius
- All the above
- Which of the following has a very low melting point
- Boron
- Gallium
- Aluminum
- Beryllium
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