Miscellaneous Periodic Properties | Inorganic Chemistry PDF Download

Miscellaneous Chemical Properties

1. Periodicity of oxy acids:
(a) Acidic character of oxy acid increases from left to right in a period.
H₂CO₃ < HNO₃ < H2SO₄ < HClO₄
(b) Acidic character of oxy acid decreases from top to bottom in a group.
HN0₃ > H₃PO₃

2. Periodicity of nature of oxide:
(a) On moving from left to right in a period, acidic nature of oxide generally increases.
e.g. CO₂ < P₂O₃ < SO₂ < CIO₂
(b) On moving from top to bottom in a group, acidic nature of oxide generally decreases.
N0₂ > P₂O₃> As₂O₃

3. Periodicity of nature of hydroxide:
(a) On moving from left to right in a period, basic nature of hydroxide generally decreases.
e.g. KOH > Ca(OH)₂  > Fe(OH)₂ > Zn(OH)₂
(b) On moving from top to bottom in a group, basic nature of hydroxide generally decreases.
LiOH < NaOH < KOH < RbOH

4. Solubility of salt in water:

• The hydration energy exhibits a decreasing trend when moving along a group.
• A decrease in lattice energy is observed along a group.

Trends In Physical Properties

• Physical properties are generally influenced by atomic weight, but exceptions can be observed, leading to irregular trends in the graph.
• Exceptions in the graph indicate deviations from the expected pattern.
• Understanding the reasons behind these exceptions is crucial for a comprehensive analysis of physical properties.
• It implies that factors beyond atomic weight play a significant role in determining certain physical properties.
• Identifying and explaining these exceptions is essential for a more nuanced understanding of the relationships between atomic properties and physical behavior.

Some Commonly Used Terms:

Noble Gases:

• Group 18 elements are referred to as noble gases.
• Also known as inert gases due to the complete filling of their outermost ns and np orbitals, making them non-reactive under ordinary conditions.
• Exceptions include Helium (He) and the first element in the 1s orbital.

Representative Elements:

• All s and p block elements, excluding the zero group, are classified as representative elements.

Transition Elements:

• Elements in the d-block, excluding the 11B group, are termed transition elements.
• These elements span the 4th, 5th, 6th, and 7th periods, residing between s and p block elements.

Inner Transition Elements:

• F-block elements, specifically 4f and 5f block elements, are known as inner transition elements.
• Comprising a total of 28 elements, they are situated in the 111B group and occupy the lower portion of the periodic table.

Typical Elements:

• Elements belonging to the second and third periods are categorized as typical elements.

Diagonal Relationship:

• Properties of elements in the second period share similarities with those in the third period.
• This type of relation between two periods, where properties resemble each other, is termed a diagonal relationship.

(i) Resemblance between Li and Mg :

• Lithium, unlike other group members, reacts with N₂ to form a nitride, mirroring the behavior of magnesium.
• When heated, lithium hydroxide, carbonate, and nitrate undergo decomposition, yielding Li₂O, similar to magnesium. However, unlike other alkali hydroxides and carbonates, lithium nitrate decomposes to form nitrite.
• Lithium hydroxide, carbonate, and fluoride exhibit higher solubility compared to their sodium and potassium counterparts. The solubilities are akin to the corresponding magnesium compounds.

ii) Resemblance between Be and Al:

• Ionic radius of Be²⁺ is comparable to that of Al³⁺ ions.
• Similar to aluminum, beryllium remains resistant to acid attacks due to the presence of a protective oxide film.
• Beryllium, like aluminum, forms a beryllate ion [Be(OH)₄]²⁻ when dissolved in alkali.
• BeO and Al₂O₃ are hard, high-melting, insoluble solids. Both oxides and their hydroxides exhibit amphoteric behavior, dissolving in sodium hydroxide solution.
• Beryllium and aluminum form stable fluoro complexes (BeF₄^2- and AlF₆^3-) in solution, while other Group 2 metals do not.
• Beryllium chloride (BeCl₂) and aluminum trichloride (Al₂Cl₆) are essentially covalent with bridged polymeric structures. Both chlorides are soluble in organic solvents and act as strong Lewis acids.

(iii) Resemblance between B and Si :

• Boron and silicon hydrides spontaneously catch fire when exposed to air and are easily hydrolyzed.
• Boron halides, like silicon halides, undergo hydrolysis in water, while aluminum halides are only partially hydrolyzed.
• Boron forms binary compounds with various metals called borides, similar to silicon forming metal silicides. Some borides and silicides undergo hydrolysis, yielding boron and silicon, respectively.
• B₂O₃ and SiO₂ exhibit acidic properties. Borates and silicates have tetrahedral B0₄ and Si0₄ structural units. Borosilicates are known where boron can replace silicon in a three-dimensional lattice. However, boron can also form planar BO₃ units.
• Both boron (B) and aluminum (Al) are semiconductors.

SUMMARY OF PERIODICITY

• Electron shells - Along the group, number of electrons remains the same and along the period, shells are increased by 1
• Valence electrons- Along the group, valence electrons increases by one and along the period, remains the same
• Electronegativity- Increases along the group and decreases along the period
• Ionization energy- Along the group, it increases and decreases along the period
• Electron Affinity- Along the group it increases and along the period decreases
• Metallic characteristics- Along the group, non-metallic characteristic increases and along the period metallic characteristics increases.
• Acidic nature of oxides increases along the group and decreases along the period
• Reducing nature of hydride increases in a period and decreases in a group.