Inorganic Chemistry: p-Block Elements - SS3 Chemistry Past Questions and Answers - page 2

Group 15 elements, also known as the Nitrogen family, include nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi). These elements share common characteristics but also exhibit distinct properties.

Properties and Trends:

1.    Atomic Structure: The elements in Group 15 have five valence electrons in their outermost energy level, leading to the common oxidation state of -3. They form covalent compounds with nonmetals and ionic compounds with metals.

2.    Atomic and Ionic Radii: As we move down the group, the atomic and ionic radii increase. This trend is attributed to the addition of new energy levels with increasing atomic numbers.

3.    Electronegativity: Electronegativity decreases down the group due to the increasing atomic size. Nitrogen, being the smallest element, has the highest electronegativity among the group.

4.    Melting and Boiling Points: Nitrogen and phosphorus are gases at room temperature, arsenic and antimony are metalloids, and bismuth is a metal. The melting and boiling points increase down the group due to the strengthening of metallic bonding.

5.    Reactivity: Nitrogen is relatively inert due to its strong triple bond in N2. Phosphorus is reactive, especially the white phosphorus allotrope, which spontaneously ignites the air. As we move down, the reactivity decreases.

Importance in Biological Systems:

Group 15 elements play essential roles in biological systems:

●     Nitrogen is a crucial component of amino acids, proteins, and nucleic acids (DNA and RNA).

●     Phosphorus is a key constituent of nucleotides, ATP (adenosine triphosphate), and phospholipids in cell membranes.

●     Antimony and bismuth compounds have been used as treatments for certain parasitic infections.

Industrial Applications:

●     Nitrogen is used in the Haber process to produce ammonia, a vital component of fertilisers and various chemical products.

●     Phosphorus is used in fertilisers, detergents, and flame retardants.

●     Arsenic compounds find applications in semiconductors and wood preservatives.

●     Bismuth is used in alloys and pharmaceuticals, such as Pepto-Bismol.

Group 16 elements, known as the Oxygen family, include oxygen (O), sulphur (S), selenium (Se), tellurium (Te), and polonium (Po). These elements exhibit a range of characteristics and form diverse allotropes.

Characteristics:

1.    Atomic Structure: Group 16 elements have six valence electrons, leading to an oxidation state of -2. They readily gain two electrons to form stable -2 ions.

2.    Electronegativity: Electronegativity decreases down the group due to increasing atomic size, with oxygen being the most electronegative nonmetal.

3.    Allotropes: Allotropes are different forms of the same element with varying molecular structures.

Allotropes and Applications:

1.    Oxygen (O2): Oxygen gas is essential for respiration in living organisms and combustion processes. It is widely used in medical settings to support patients with respiratory issues.

2.    Sulphur (S8): Sulphur exists as S8 rings and has various applications. It is used in the vulcanization of rubber, production of sulfuric acid (an essential industrial chemical), and the pharmaceutical industry.

3.    Selenium (Se): Selenium is used in photocells, glassmaking, and electronics. It is also an essential trace element for various organisms.

4.    Tellurium (Te): Tellurium is used in alloys, as a colouring agent in ceramics, and in the electronics industry.

5.    Polonium (Po): Polonium is radioactive and highly toxic. It is primarily used in scientific research, particularly in particle physics and as a neutron source.

Overall, the diverse allotropes and characteristics of Group 16 elements make them valuable in numerous applications, ranging from industrial processes to technological advancements. However, some of these elements, especially polonium, require careful handling due to their radioactive and toxic nature.