Group 14 Elements (Carbon Family) - Practice Questions & MCQ

Electronic Configuration
The valence shell electronic configuration of these elements is ns²np². The inner core of the electronic configuration of elements in this group also differs.

Covalent Radius
There is a considerable increase in covalent radius from C to Si, thereafter from Si to Pb a small increase in radius is observed. This is due to the presence of completely filled d and f orbitals in heavier members.

Ionization Enthalpy
The first ionization enthalpy of group 14 members is higher than the corresponding members of group 13. The influence of inner core electrons is visible here also. In general, the ionisation enthalpy decreases down the group. The small decrease in ∆_iH from Si to Ge to Sn and slight increase in ∆_iH from Sn to Pb is the consequence of poor shielding effect of intervening d and f orbitals and increase in size of the atom.

Electronegativity
Due to small size, the elements of this group are slightly more electronegative than group 13 elements. The electronegativity values for elements from Si to Pb are almost the same.

Allotropy
The ability of an element to exist in more than one physical form is called allotropy. All the elements of this group except Pb exhibit allotropy. Carbon has three allotropes i.e, diamond, graphite and fullerene

Valency
All the elements of this group show tetravalency as they have 4 electrons in their valence shell.

Atomic and Ionic radii
As we move down the group, the radius of these elements increases.

Multiple Bonding
Carbon forms p-p bonding with itself and with S, N and O. While the other elements of this group form p-d bonding as they have a vacant d-orbital while carbon does not have.

Hydrides

• All the members of this group form covalent hydrides.
• Hydrides of carbon are called hydrocarbon.
• Hydrides of Si and Ge are known as silanes and germanes.
• Thermal stability of hydrides decreases down the group.
• Reducing character increases down the group.

Halides
These elements can form halides of formula MX₂ and MX₄ (where X = F, Cl, Br, I). Except carbon, all other members react directly with halogen under a suitable condition to make halides. Most of the MX₄ are covalent in nature. The central metal atom in these halides undergoes sp³ hybridisation and the molecule is tetrahedral in shape. Exceptions are SnF₄ and PbF₄, which are ionic in nature. PbI₄ does not exist because Pb—I bond initially formed during the reaction does not release enough energy to unpair 6s² electrons and excite one of them to higher orbital to have four unpaired electrons around lead atom. Heavier members Ge to Pb are able to make halides of formula MX₂. Stability of dihalides increases down the group. Considering the thermal and chemical stability, GeX₄ is more stable than GeX₂, whereas PbX₂ is more than PbX₄. Except CCl₄, other tetrachlorides are easily hydrolysed by water because the central atom can accommodate the lone pair of electrons from oxygen atom of water molecule in d orbital.

All members when heated in oxygen form oxides. There are mainly two types of oxides, i.e., monoxide and dioxide of formula MO and MO₂ respectively. SiO only exists at high temperature. Oxides in higher oxidation states of elements are generally more acidic than those in lower oxidation states. The dioxides — CO₂, SiO₂ and GeO₂ are acidic, whereas SnO₂ and PbO₂ are amphoteric in nature. Among monoxides, CO is neutral, GeO is distinctly acidic whereas SnO and PbO are amphoteric.