Grade 11
  1. Basic concepts of chemistry  1.1. Importance of Chemistry  1.2. Nature and scope of chemistry  1.3. laws of chemical combination  1.3.1. Law of conservation of mass  1.3.2. Law of definite proportions  1.3.3. Law of multiple proportions  1.3.4. Law of gaseous volume  1.3.5. Avogadro's Law  1.4. Dalton's atomic theory  1.5. Mole concept and molar mass  1.6. Percent composition  1.7. Empirical and molecular formula  1.8. Stoichiometry and Stoichiometric Calculations  1.9. Limiting reagent concept
  2. Structure of the atom  2.1. Discovery of the electron, proton, and neutron  2.2. Atomic Model  2.2.1. Thomson's model  2.2.2. Rutherford's model  2.2.3. Bohr's model  2.3. Quantum mechanical model of the atom  2.4. Dual nature of matter and radiation  2.5. Heisenberg's uncertainty principle  2.6. Quantum numbers  2.7. Atomic orbitals and their shapes  2.8. Electronic configuration of elements  2.9. Aufbau principle  2.10. Pauli's exclusion principle  2.11. Hund's maximum multiplicity rule  2.12. de Broglie's hypothesis  2.13. Photoelectric effect
  3. Classification of elements and periodicity in properties  3.1. Historical development of the periodic table  3.2. Modern Periodic Law and Periodic Table  3.3. Periodic trends in properties  3.3.1. Atomic and Ionic Radius  3.3.2. Ionization enthalpy  3.3.3. Electron gain enthalpy  3.3.4. Electronegativity  3.3.5. Valency  3.3.6. Metallic and Non-Metallic Properties  3.3.7. Oxidation states  3.4. Unusual Properties of the First Elements
  4. Chemical Bonding and Molecular Structure  4.1. Kossel–Lewis approach to chemical bonding  4.2. Ionic or electrovalent bond  4.3. Covalent bond and its features  4.4. Bond parameters  4.5. VSEPR Theory  4.6. Valence bond theory  4.7. Hybridization and its types  4.8. Molecular orbital theory  4.8.1. Bond order and stability  4.9. Hydrogen bonding
  5. States of matter  5.1. Intermolecular forces  5.2. Gas Laws  5.2.1. Boyle's law  5.2.2. Charles's Law  5.2.3. Avogadro's Law  5.2.4. Dalton's law of partial pressure  5.2.5. Graham's law of spread  5.3. Ideal Gas Equation and Applications  5.4. Real gases and deviations from ideal behaviour  5.5. Kinetic molecular theory of gases  5.6. Liquefaction of gases  5.7. Properties of Liquids  5.8. Surface tension and viscosity
  6. Thermodynamics  6.1. System and environment  6.2. Types of systems in thermodynamics  6.3. Types of procedures  6.4. First law of thermodynamics  6.5. Internal energy and enthalpy  6.6. Heat capacity and specific heat  6.7. Hess's law of constant heat summation  6.8. Bond dissociation enthalpy  6.9. Enthalpy of formation and combustion  6.10. Enthalpy of solution and neutralization  6.11. Spontaneity and the second law of thermodynamics  6.12. Gibbs free energy and its applications
  7. Balance  7.1. The concept of balance  7.2. Equilibrium constant and its applications  7.3. Le Chatelier's principle  7.4. Ionic equilibrium in solutions  7.5. Acid and Base Theory  7.5.1. Arrhenius concept  7.5.2. Bronsted-Lowry concept  7.5.3. Lewis concept  7.6. pH Scale and pOH  7.7. Common ion effect  7.8. Hydrolysis of salts  7.9. Buffer solutions and their mechanism of action  7.10. Solubility equilibrium of sparingly soluble salts
  8. Redox reactions  8.1. Oxidation and reduction concepts  8.2. Oxidation number and its applications  8.3. Redox reactions in terms of electron transfer  8.4. Balancing redox reactions (oxidation number and ion-electron methods)  8.5. Types of redox reactions  8.6. Electrochemical Cells and Redox Reactions
  9. Hydrogen  9.1. Position of Hydrogen in the Periodic Table  9.2. Isotopes of hydrogen  9.3. Preparation of Hydrogen  9.4. Properties of Hydrogen  9.5. Hydrides and their classification  9.6. Water and heavy water  9.7. Hydrogen peroxide and its properties  9.8. Uses of Hydrogen and Its Compounds
  10. S-block elements (alkali and alkaline earth metals)  10.1. Group 1 Elements - Properties and Trends  10.2. Group 2 Elements - Properties and Trends  10.3. Unusual properties of lithium and beryllium  10.4. Important compounds of sodium and their uses  10.5. Important Compounds of Magnesium and Calcium
  11. Some p-block elements  11.1. General Introduction to p-Block Elements  11.2. Group 13 Elements  11.2.1. Boron and its compounds  11.3. Group 14 Elements  11.3.1. Carbon and its allotropes  11.3.2. Important Compounds of Carbon and Silicon
  12. Organic Chemistry - Some Basic Principles and Techniques  12.1. Classification and Nomenclature of Organic Compounds  12.2. Structural representation of organic compounds  12.3. Classification of organic reactions  12.4. Electronic Effects in Organic Chemistry  12.4.1. Inductive effect  12.4.2. Resonance effect  12.4.3. Hyperconjugation  12.5. Reaction mechanism and intermediate species  12.6. Purification and qualitative analysis of organic compounds
  13. Hydrocarbons  13.1. Hydrocarbons  13.1.1. Preparation and Properties of Alkenes  13.2. alkene  13.2.1. Preparation and Properties of Alkenes  13.2.2. Electrophilic addition reactions  13.3. Alkynes  13.3.1. Preparation and Properties of Alkynes  13.4. Aromatic hydrocarbons  13.4.1. Structure and properties of benzene  13.4.2. Electrophilic substitution reactions of benzene
  14. Environmental Chemistry  14.1. Environmental Pollution  14.2. Atmospheric pollution and the greenhouse effect  14.3. Water pollution and treatment methods  14.4. Soil pollution and its effects  14.5. Industrial waste and its treatment  14.6. Strategies for pollution control

Grade 11 → S-block elements (alkali and alkaline earth metals) ↓


Unusual properties of lithium and beryllium


The s-block elements of the periodic table comprise the groups consisting mainly of alkali metals and alkaline earth metals. These include elements such as lithium (Li) in group 1 and beryllium (Be) in group 2. Interestingly, lithium and beryllium, the first members of their respective groups, exhibit some unique properties that set them apart from the other members. This document discusses the unusual behaviour of lithium and beryllium in detail, and explores the causes and implications of these peculiarities.

Understanding the s-block elements

Before exploring the specific properties of lithium and beryllium, it is important to establish a basic understanding of the general characteristics of the alkali metals and alkaline earth metals.

Alkali metals (Group 1 elements)

Alkali metals are located in group 1 of the periodic table. They include these elements:

  • Lithium (Li)
  • Sodium (Na)
  • Potassium (K)
  • Rubidium (Rb)
  • Caesium (Cs)
  • Francium (Fr)

These elements have one electron in their outermost shell, so their usual valency is +1. They are known for:

  • Highly reactive, especially with water.
  • Soft with low melting point.
  • Good conductors of electricity due to the presence of freely moving valence electrons.

Alkaline earth metals (Group 2 elements)

The alkaline earth metals are found in group 2 of the periodic table. The elements include:

  • Beryllium (Be)
  • Magnesium (Mg)
  • Calcium (Ca)
  • Strontium (Sr)
  • Barium (Ba)
  • Radium (Ra)

These elements have two electrons in their outer shell, resulting in a normal valency of +2. Key characteristics include:

  • Lower reactivity than alkali metals.
  • High melting point and hardness.
  • To form basic oxides and hydroxides.

Unique properties of lithium

Although Lithium is classified as an alkali metal, it has several properties that are different from other members of its group. Let's explore these properties:

Small size and high density

Lithium is the lightest metallic element, yet, its atomic and ionic size is relatively small compared to other alkali metals. This is due to the following points:

  • Possession of only two electrons as opposed to other alkali metals which have more electrons.
  • The greater effective nuclear charge coupled with less dispersion of the electron cloud makes it denser.

The consequences of lithium being too small in size are shown in the following example.

Li < Na < K < Rb < Cs

Visual example of atomic size:

Took No K

High ionization energy

The ionization energy of lithium is higher than that of other alkali metals. This is because:

  • The electrons are more tightly bound as a result of the smaller atomic size.
  • The greater effective nuclear charge increases the energy required to remove the electron.

As a result, lithium does not impart color to the flame, whereas other alkali metals do, because they are easily excited with low ionization energies.

Low reactivity

Lithium is less reactive with water and oxygen than the other alkali metals. For example, lithium reacts with water to form hydrogen gas and lithium hydroxide, but this reaction is not as vigorous as that seen with sodium or potassium.

2 Li + 2 H2O → 2 LiOH + H2

Formation of nitrides

Unlike the other alkali metals, lithium reacts directly with nitrogen to form lithium nitride.

6 Li + N2 → 2 Li3N

This feature makes lithium even more unique because it can react directly with nitrogen under standard conditions.

Unusual behavior in compounds

Compounds of lithium, such as lithium chloride (LiCl), are somewhat covalent in nature rather than purely ionic. Consider these points:

  • High polarization power of small lithium ions.
  • Increase in covalent nature due to concentration of positive charge.

Unique properties of beryllium

Beryllium, although one of the alkaline earth metals, exhibits unusual behaviour, quite different from its nearest neighbours magnesium or calcium.

High ionization energy

The first ionization energy of beryllium is the highest among the group 2 elements:

  • Small atomic size results in high ionization energy.
  • The valence electrons are strongly bound due to the effective nuclear charge.

The trends in ionization energy can be represented visually by considering increasing atomic number:

Be > Mg > Ca > Sr > Ba

Visual example of ionization energy:

Non-metallic behaviour

Surprisingly, beryllium displays some non-metallic properties that are not typical of its metallic group:

  • Relatively low density compared to other members of group 2.
  • Its high ionization energy and small atomic radius leads to the formation of covalent bonds rather than ionic bonds.

No reaction with water

Beryllium does not react with water or steam, further highlighting its unique position among the alkaline earth metals.

Unusual compounds

Compounds formed by beryllium, such as beryllium chloride, are covalent and exhibit some nonmetallic characteristics:

  • Beryllium oxide (BeO) and beryllium hydroxide (Be(OH)2) are amphoteric.
  • Beryllium chloride (BeCl2) is soluble in organic solvents.

These properties arise from the high polarizability of the ion, which is due to its small size and relatively high nuclear charge, thus promoting the formation of covalent compounds rather than ionic compounds.

Diagonal relationship - lithium and magnesium

A diagonal relationship has been observed between selected pairs of diagonally adjacent p block and s block elements in the periodic table, particularly between lithium (Li) and magnesium (Mg). These two elements, though in different groups, exhibit similar behaviour.

Similar properties

Both Lithium and Magnesium have the following similarities:

  • Formation of Nitride: Both react directly with nitrogen to form their respective nitrides, Li3N and Mg3N2.
  • Solubility Pattern: LiCl and MgCl2 are soluble in organic solvents.
  • Decomposition reactions: Li2CO3 and MgCO3 decompose on heating.

Visual depiction of diagonal relationships:

Took Milligrams

Conclusion

The unique properties of lithium and beryllium arise from their atomic and electronic structures. Their anomalies compared to other group members can be routinely interpreted in light of atomic size, ionization energy, polarization strength, and metallic versus non-metallic properties. The diagonal relationship between lithium and magnesium is another example of how their individual characteristics can exhibit similarities with metals from other groups. Understanding these peculiarities enables us to appreciate the delicate intricacies of the periodic table and the fascinating world of chemical behavior.


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Unusual properties of lithium and beryllium

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