Name: Periodic Trends of Valency and Oxidation States
Uploaded: 2019-07-19
Duration: 28 min 2 s
Description: Each element is said to have a valency that determines its combining capacity with other elements. Watch this video to learn about the periodic trends in val...

Question

Give a comparative account of Group

14

elements (Carbon family) of the periodic table.

Accepted Answer

The group $14$ elements are the second group in the $p$ -block of the periodic table. It is also called the carbon group. The members of this group are Carbon $(C)$ , Silicon $(Si)$ , Germanium $(Ge)$ , Tin $(Sn)$ , Lead $(Pb)$ .

Electronic Configuration of Group $14$ Elements
The group $14$ elements have a general electronic configuration of ${ns}^{2} {np}^{2}$ . These elements have two electrons in the outermost $p$ orbitals. As all the elements in group $14$ have $4$ electrons in the outermost shell, the valency of group $14$ elements is $4$ . They use these electrons in the bond formation in order to obtain octet configuration.

Oxidation States and Inert pair Effect of Group $14$ Elements
The general oxidation states exhibited by the group $14$ elements are $+ 4$ , and $+ 2$ .

As we go down the group, the tendency to form $+ 2$ ion increases. This is due to inert pair effect. This effect is exhibited by $p$ -block elements. This can be explained using the inert pair effect. It is the non-participation of the s-orbital during bonding due to the poor shielding of the intervening electrons.

For elements like $Sn$ and $Pb, d$ and $f$ orbitals are filled with electrons. Since the shielding ability of $d$ and $f$ orbitals are very poor, the nuclear charge that seeps through attracts the $s$ orbital closer to the nucleus. This makes the $s$ orbital reluctant to bond, thereby only the $p$ electrons involved in bonding. Therefore, ${Pb}^{4 +}$ is a very good oxidizing agent.

Anomalous Behaviour of Carbon
Carbon exhibits different behaviour from the rest of the group due to,

Small Size

High Electronegativity

High Ionization Enthalpy

Absence of d-orbital in the Valance Shell

Chemical Properties of Group $14$ Elements
Covalent Radii
The radii of group $14$ elements are lesser than that of group $13$ elements. This can be explained by the increase in the effective nuclear charge.

The increase in the radii from $C$ to $Si$ is considerable, after which the increase in the radii is less. This can be attributed to the poor shielding of $d$ and $f$ orbitals, which increase the effective nuclear charge, thereby making the radii small.

Ionization Enthalpy
The ionization energy of group $14$ elements is greater than that of group $13$ elements. This can be attributed to size.

Down the group, the Ionization Enthalpy decreases. There is a sharp decrease from $C$ to $Si$ , after which the decrease is nominal.

The order is as follows, $C > Si > Ge > Pb > Sn$

Here $Pb$ has a greater ionization enthalpy than $Sn$ due to ineffective shielding of $d$ and $f$ orbitals.

Physical Properties:
Metallic Character
Group $14$ elements are less electropositive than group $13$ owing to their small size and high ionization enthalpy.

Down the group, the metallic character increases. $C$ and $Si$ are non-metals, $Ge$ a metalloid, and $Sn$ and $Pb$ are soft metals with low melting points.

Melting and Boiling Points
The melting and boiling point of carbon, silicon, and germanium is significantly high because they have a very stable solid structure. Tin and Lead have a lower melting point because only two bonds are formed instead of four, due to inert pair effect.

The melting point of carbon is extremely high. All the elements of group-14 possess diamond-type lattice structure which is highly stable in nature. The process of melting results in the breakage of these highly stable lattice structures.

Down the group, the melting point decreases as the $M - M$ bonds are reduced as the size of the atoms increases. Since, Tin and lead are metals therefore, the melting points of these elements are much lower.

Give a comparative account of Group $14$ elements (Carbon family) of the periodic table.

Important Questions on The Carbon Family (Group-14 Elements)

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