UNIT 11 THE p-BLOCK ELEMENTS
GROUP 13 ELEMENTS: THE BORON FAMILY
Elements: Boron, Aluminium, Gallium, Indium, Thallium
Electronic configuration: The outer electronic configuration of these elements is ns2 np1.
Atomic radii: Atomic radii increase on going down the group.
Ionization enthalpies: The ionization enthalpies do not decrease smoothly down the group.
Electronegativity: Down the group, electronegativity first decreases from B to Al and then increases marginally.
- Boron is non-metallic in nature. It is extremely hard and black coloured solid. It has an unusually high melting point.
- Rest of the members are soft metals with low melting point and high electrical conductivity.
- Density of the elements increases down the group from boron to thallium.
- Reactivity towards air: With oxygen, these elements form their respective oxides. With dinitrogen, they from nitrides.
- Reactivity towards acids and alkalis: Boron does not react with acids and alkalis but aluminium dissolves in mineral acids and aqueous alkalis.
- Reactivity towards halogens: These elements react with halogens to form trihalides.
GROUP 14 ELEMENTS: THE CARBON FAMILY
Elements: Carbon, Silicon, Germanium, Tin, Lead
Electronic configuration: The valence shell electronic configuration of these elements is ns2 np2.
Covalent radius: There is a considerable increase in covalent radius from C to Si. From Si to Pb, there is a small increase in radius.
Ionization enthalpy: The first ionization enthalpy of group 14 members is higher than the corresponding members of group 13.
Electronegativity: The elements of this group are slightly more electronegative than group 13 elements.
- All the elements of this group are solid.
- Melting points and boiling points of group 14 elements are much higher than those of corresponding elements of group 13.
- Reactivity towards oxygen: All members when heated with oxygen form oxides.
- Reactivity towards water: Carbon, silicon, germanium and lead are unaffected by water but tin forms its dioxide and dihydrogen gas.
- Reactivity towards halogen: They form halides with halogens.