Introduction to group 14 elements

Introduction

Carbon, silicon, germanium, tin, lead and Flerovium are elements in group 4A. Carbon and silicon are the most important elements in the universe. Carbon is the fundamental element in the molecules of all living things while silicon is the fundamental element in the geologic world. The two familiar allotropes of carbon are graphite and the diamond. Carbon consists of three isotopes that are known. These are 12C, 13C and 14C.  Research has shown that Carbon-14 is a more radioactive isotope with a half-life of 5770 years and is mainly used for carbon dating of fossils. The main ore of tin is cassiterite and lead mainly exists as galena.

 

Element

Symbol

Atomic #

Atomic Mass

Classification

Electron Configuration

Carbon

C

6

12.011

Non-metal

[He]2s22p2

Silicon

Si

14

28.0855

Metalloid

[Ne]3s23p2

Germanium

Ge

32

72.61

Metalloid

[Ar]3d104s24p2

Tin

Sn

50

118.710

Metal

[Kr]4d105s25p2

Lead

Pb

82

207.2

Metal

[Xe]4f145d106s26p2

Flerovium

Fl

114

287

Metal

[Rn]5f146d107s27p2

 

Electron configuration

Group 4A elements have the outer electron configuration of ns2np2.

 

Ionization energy

It is beyond doubt that the first ionization energy of group 4A elements is greater than the corresponding elements of group 3A. From our previous discussion, the influence of inner core electron is also visible in group 4A. As you move down the group, ionization energy decreases. Due to the poor shielding power of the d and f-orbitals, there is a small decrease in ionization energy from silicon while the tin turns into germanium with a small increase in first ionization energy from tin to lead.

 

Electronegativity of group 4A elements

Group 4A elements are slightly more electronegative than the corresponding group 3A due to their small size. Silicon, germanium and tin have the same electronegativity value.

 

Physical properties of group 4A

Group 4A elements are all solids at room temperature. Both silicon and carbon are non-metals. Germanium is a metalloid while tin and lead are metals with very low melting points. The boiling and melting points of group 3A elements is lower than those of group 4A elements.

 

Chemical properties of group 4A

Oxidation state and trends in the reactivity of group 4A

The oxidation state of group 4A elements is +4 and + 2 since these elements have four electrons in the outermost energy level. The elements with +4 oxidation state are mainly covalent in nature because the total o the 1st four ionization energy is very high. The probability of heavy elements in the group such as germanium, tin and lead to show lower oxidation state is high due to the inability of the ns2 electrons to participate in bonding.  The stability of these oxidation states changes as one moves down the group. Carbon can’t exceed it`s covalence more than four. However, the remaining members of group 4A can do so because of the presence of the d orbital in their structures. For this reason, group 4A members except carbon form halides which hydrolysis in water to form complex compounds by receiving electrons from donor species.

 

Reaction of group 4A with air

Group 4A elements form the oxides when heated in oxygen.  They react with oxygen to form dioxides and monoxides. Silicon oxides can only exist at high temperatures. We should note that dioxides are more acidic in nature as compared to monoxides. Carbon dioxide, silicon dioxide and germanium oxide are acidic whereas tin dioxide and lead dioxides are amphoteric.

 

Reaction of group 4A with water

Tin decomposes steam to produce tin dioxide and hydrogen gas. The remaining members of group 4A don’t react with water.

 

Reaction of group 4A with halogens

Group 4A react with halogens to form both MX2 and MX4 halides. All group 4A elements except carbon react with halogens to yield halides. Generally, MX4 halides are covalent in nature except those of SnF4 and PbF4 which are mainly ionic compounds.MX2 compounds are majorly formed by heavier elements in the group germanium to lead.

NOTE: Lead (IV) iodide doesn’t exist since the Pb-I bond formed is unable to release more energy to unpair the 6s2 electrons and be able to excite one of them to the higher orbital to have four unpaired electrons around the lead atom.

 



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