4. Elements of group 13. Properties and trends of elements of group 13 Francisco Javier Cervigon Ruckauer

4. Elements of group 13

Properties and trends of elements of group 13

ELEMENTS OF GROUP 13


























PHYSICAL PROPERTIES OF ELEMENTS FROM GROUP 13

As we introduced in last unit, boron exhibits mostly nonmetallic behavior and is therefore classified as a semimetal atom. However, the other members of Group 13 are clearly considered as metals although they exhibit a less pronounced electropositive character than block-s metals. Boron is the most electronegative element and the electronegativity decreases as you move down in the group. The size of elements of group 13 is smaller than that observed for alkaline-earth metals due to the increase in nuclear effective charge. The radius of the elements increases as you go down in the group with the exception of Gallium which is slightly smaller than aluminium. This is attributed to the presence for gallium of electrons in 3d orbitals which do not screen the higher positive charge in the nucleus effectively, and therefore electrons are more attracted and consequently the radius decreases.
Elements of group 13 have no simple pattern in the melting points given that each element in the group is organized in a different way in the solid phase. For instance, as it has been shown before, one of the four allotropes of boron forms icosahedral clusters of 12 atoms, while aluminium adopts a face-centered cubic structure, but gallium forms a unique structure containing pairs of atoms. Indium and thallium each form other, different structures. Contrarily, their boiling points do show a decreasing trend as the mass of the elements increases, given the fact that once the elements are melted and the crystal arrangements disorganised, the metallic bond becomes weaker. Additionally, the increase in mass per unit volume is the cause for the increase of density as you move down in the group. The low density of aluminium is notable, which gives it an extraordinary use in light alloys for constructing aircraft, cars and ships.


CHEMICAL PROPERTIES OF ELEMENTS FROM GROUP 13


























Francisco Javier Cervigon Ruckauer

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