What are Group 14 Elements?
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)
- Flerovium (Fl)
Table of Content
- Electronic Configuration
- Oxidation States
- Anomalous Behaviour of Carbon
- Chemical Properties
- Physical Properties
- Compounds of Group 14 Elements
Electronic Configuration of Group 14 Elements
The group 14 elements have a general electronic configuration of ns2np2. These elements have 2 electrons in the outermost p orbitals. The electronic configuration of these elements is shown below:
Group 14 Elements
|2nd||Carbon (C)||6||[He]2s2 2p2|
|3rd||Silicon (Si)||14||[Ne]3s2 3p2|
|4th||Germanium (Ge)||32||[Ar]3d10 4s2 4p2|
|5th||Tin (Sn)||50||[Kr]4d10 5s2 5p2|
|6th||Lead (Pb)||82||[Xe]4f14 5d10 6s2 6p2|
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.
⇒ Check: List of all periodic table elements
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, Pb4+ is a very good oxidizing agent.
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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
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.
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.
⇒ Check: s-block elements
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. Sn and Pb 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.
Four Covalent Compounds:
Four covalent compounds are compounds in which the four electrons in the valence shell play an active role in bonding. Most of the group 14 element possesses this property.
Compounds formed by Group 14 Elements
Hydrides of Group 14:
All of the elements of group 14 form hydrides. Carbon forms hydrides extensively due to their ability to catenate. The hydrides of carbon are categorized as below
- Alkanes (paraffin’s): General formula: CnH2n+2
- Alkenes (olefins): General formula: CnH2n
- Alkynes (Acetylenes): General formula: CnH2n-2
- Aromatic compounds
- Silicon forms hydrides having the general formula SinH2n+2 and are called silanes.
- Germanium forms hydrides of the form GenH2n+2, where nmax=5 and are called germanes.
- Tin forms SnH4 and are called stannane. It is much less stable.
Oxides of Group 14:
Group 14 elements form oxides of the type MO and MO2. Lead also form an oxide Pb3O4 which is a mixed oxide of PbO and PbO2. Among the monoxides, CO is neutral, GeO is basic while SnO and PbO are amphoteric.
In CO2, C is sp hybridised. It is different from SiO2 in which Si is sp3 hybridised. In SiO2, each O atom is bonded to two Si bonds. This gives rise to a three-dimensional structure for SiO2. This also attests to the high melting point of SiO2.
Among the dioxides, the acidic character decreases down the group. CO2 is the most acidic and PbO2 being the most basic amongst the dioxides.
⇒ Also Read: Allotropes of Carbon
Halides of Group 14:
They form tetrahalides of the form MX4. The central atom is sp3 hybridized and assumes a tetrahedral shape.
Note: Elements below C, have empty d-orbitals, with which they can exhibit back bonding with the halogens ( pπ-dπ)
Carbon does not form dihalides. The dihalides are sp2 hybridized and have a bent shape.
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