Undergraduate
  1. General chemistry  1.1. Introduction to Chemistry  1.2. Atomic Structure  1.2.1. Subatomic particles  1.2.2. Atomic Model  1.2.3. Quantum numbers  1.2.4. Electron Configuration  1.2.5. Periodic trends  1.2.6. Isotopes and their applications  1.3. Chemical bond  1.3.1. Ionic bond  1.3.2. Covalent bonds  1.3.3. Metal Bond  1.3.4. Hybridization  1.3.5. Molecular geometry and VSEPR theory  1.3.6. Bond polarity and dipole moment  1.4. Stoichiometry  1.4.1. Mole concept  1.4.2. Empirical and molecular formula  1.4.3. Limiting reactant and excess reactant  1.4.4. Percent Yield and Purity  1.4.5. Dilution calculation  1.5. States of matter  1.5.1. Gas Laws  1.5.2. Matter and Intermolecular Forces  1.5.3. Solid and Crystal Structures  1.5.4. Phase diagram  1.5.5. Plasma and supercritical fluid  1.6. Chemical reactions  1.6.1. Types of Chemical Reactions  1.6.2. Balancing Chemical Equations  1.6.3. Thermochemical reactions  1.6.4. Reaction energy profiles  1.7. Solutions and Mixtures  1.7.1. Concentration units  1.7.2. Syndrome properties  1.7.3. Solubility and Solubility Rules  1.7.4. Henry's Law and Raoult's Law  1.7.5. Partition coefficient  1.8. Chemical equilibrium  1.8.1. Law of mass action  1.8.2. Le Chatelier's principle  1.8.3. Reaction quotient  1.8.4. To use this online calculator for Equilibrium Constant, enter Equilibrium Constant (Eq.) and hit the calculate button. Here is how the Equilibrium Constant calculation can be explained with given input values -> 0.05 = 0.05/0.  1.8.5. Acid-base balance  1.9. Acids and bases  1.9.1. Arrhenius, Brønsted–Lowry, and Lewis definitions  1.9.2. pH and pOH  1.9.3. Acid-base titration  1.9.4. Buffer Solution  1.9.5. Acid-base indicator  1.9.6. Polyprotic Acids and Bases  1.10. Electrochemistry  1.10.1. redox reactions  1.10.2. Galvanic and Electrolytic Cells  1.10.3. Nernst equation  1.10.4. Electrolysis  1.10.5. Faraday's laws of electrolysis  1.11. Thermodynamics  1.11.1. Laws of Thermodynamics  1.11.2. Enthalpy, entropy and Gibbs free energy  1.11.3. Spontaneity of reactions  1.11.4. Thermodynamic cycles (Hess's law, Carnot cycle)  1.12. Kinetics  1.12.1. Rate law and reaction order  1.12.2. Activation Energy and Catalyst  1.12.3. Collision theory  1.12.4. Reaction mechanism  1.12.5. Transition state theory
  2. Organic chemistry  2.1. Structure and relationships  2.1.1. Hybridisation in Carbon Compounds  2.1.2. Resonance and aromatization  2.1.3. Molecular orbitals  2.1.4. Inductive and mesomeric effects  2.2. Hydrocarbons  2.2.1. Hydrocarbons  2.2.2. Alkene  2.2.3. Alkynes  2.2.4. Aromatic compounds  2.2.5. Cycloalkanes and Conformation  2.3. Functional Group  2.3.1. Alcohols and phenols  2.3.2. Ethers and epoxides  2.3.3. Aldehyde and ketone  2.3.4. Carboxylic acids and derivatives  2.3.5. Amin  2.3.6. Esters and amides  2.3.7. Thiols and sulfides  2.4. Stereoscopic  2.4.1. Isomerism in Stereochemistry  2.4.2. Chirality and optical activity  2.4.3. Structural analysis  2.4.4. Diastereomers and Enantiomers  2.5.1. Substitution reactions  2.5.2. Elimination reactions  2.5.3. Addition reactions  2.5.4. Radical reactions  2.5.5. Rearrangement reactions  2.5.6. Pericyclic Reactions  2.6. Spectroscopy and structural analysis  2.6.1. Infrared Spectroscopy  2.6.2. Nuclear magnetic resonance spectroscopy  2.6.3. Mass Spectrometry  2.6.4. UV-visible spectroscopy  2.6.5. X-ray crystallography  2.7. Polymer chemistry  2.7.1. Addition and Condensation Polymers  2.7.2. Polymerization mechanism  2.7.3. Biodegradable Polymer  2.7.4. Conducting and smart polymers
  3. Inorganic chemistry  3.1. Coordination chemistry  3.1.1. Ligands and coordination compounds  3.1.2. Crystal field theory  3.1.3. Molecular Orbital Theory in Coordination Compounds  3.1.4. Jahn–Taylor distortion  3.2. Main Group Chemistry  3.2.1. Alkali and alkaline earth metals  3.2.2. Halogens and Noble Gases  3.2.3. Transition metals and their complexes  3.2.4. Lanthanides and Actinides  3.3. Solid state chemistry  3.3.1. Crystal lattices and unit cells  3.3.2. Defects in solids  3.3.3. Electrical and magnetic properties  3.3.4. Superconductivity  3.4. Bio-inorganic chemistry  3.4.1. Metal ions in biology  3.4.2. Enzymatic reactions with metals  3.4.3. Metal poisoning and detoxification  3.4.4. Metalloproteins and Metalloenzymes
  4. Physical chemistry  4.1. Quantum Chemistry  4.1.1. Wave–particle duality  4.1.2. Schrödinger Equation  4.1.3. Quantum Numbers and Orbitals  4.1.4. Atomic and molecular spectroscopy  4.2. Statistical mechanics  4.2.1. Maxwell–Boltzmann distribution  4.2.2. Partitioning functions  4.2.3. Bose–Einstein and Fermi–Dirac statistics  4.3. Chemical thermodynamics  4.3.1. Gibbs Free Energy  4.3.2. Phase transition  4.3.3. Thermodynamic efficiency  4.4. Surface chemistry  4.4.1. Absorption and Catalysis  4.4.2. Colloids and Emulsions
  5. Analytical Chemistry  5.1. Classical methods  5.1.1. Gravimetric Analysis  5.1.2. titrimeter  5.2. Instrumental methods  5.2.1. Chromatography  5.2.2. Spectroscopy  5.2.3. Electroanalytical methods  5.2.4. X-ray diffraction
  6. Industrial Chemistry  6.1. Petrochemistry  6.2. Chemical engineering principles  6.3. Green Chemistry  6.4. Pharmaceuticals and Drug Synthesis
  7. Biochemistry  7.1. Carbohydrates  7.2. Proteins and enzymes  7.3. Lipids and membranes  7.4. Nucleic acids  7.5. Metabolism and Bioenergetics  7.6. Enzyme kinetics and mechanism

Undergraduate → Inorganic chemistry → Main Group Chemistry ↓


Halogens and Noble Gases


In the world of chemistry, the periodic table is an essential tool. It organizes all of the known elements into a meaningful array where their properties can be systematically highlighted. Within this table, certain groups of elements display common characteristics. This lesson will go deeper into two fascinating groups in main group chemistry: the halogens and the noble gases. These elements can be found in groups 17 and 18, respectively.

Halogens

The halogens belong to group 17 of the periodic table. The term "halogen" comes from the Greek words "hal-" (salt) and "-gen" (to produce), which describes the ability of these elements to produce salts. This family includes the following elements:

  • Fluorine (F)
  • Chlorine (Cl)
  • Bromine (Br)
  • Iodine (I)
  • Astatine (At)

Each of these elements is highly reactive, especially with the alkali metals and alkaline earth metals, with which they can form ionic compounds called salts.

Physical properties of halogens

  • State: Halogens exist in three states of matter at room temperature: fluorine and chlorine as gases, bromine as liquids, and iodine and astatine as solids.
  • Color: These elements have different colors due to electron transitions: fluorine is pale yellow, chlorine is greenish-yellow, bromine is reddish-brown, and iodine is purple.
  • Melting point and boiling point: There is an increasing trend in melting point and boiling point from fluorine to astatine due to the increasing strength of van der Waals forces.

Visualizing the trend

Let's look at the boiling point trend using an example:

Element: F Cl Br I At Boiling Point (°C): -188 -34 59 184 337
Element: F Cl Br I At Boiling Point (°C): -188 -34 59 184 337
F Chlorine BR I But boiling point of halogens

The trend shows that the boiling point of halogens increases going from fluorine to astatine because the size of the atom becomes larger and as a result the van der Waals forces also increase.

Chemical properties of halogens

  • Reactivity: All halogens are highly electronegative and react vigorously with metals and other elements.
  • Formation of salts: Halogens react with alkali metals to form ionic compounds, such as sodium chloride (NaCl).
  • Displacement reactions: A more reactive halogen can displace a less reactive halogen from a metal halide solution.

Text example of a displacement reaction

When chlorine gas is passed through a solution of potassium bromide (KBr), the reaction proceeds as follows:

Cl 2 (g) + 2KBr(aq) → 2KCl(aq) + Br 2 (aq)
Cl 2 (g) + 2KBr(aq) → 2KCl(aq) + Br 2 (aq)

Noble gases

The noble gases are located in group 18. Known for their lack of reactivity due to having a full valence shell, this group includes:

  • Helium (He)
  • Neon (Ne)
  • Argon (Ar)
  • Krypton (Kr)
  • Xenon (Xe)
  • Radon (Rn)

Physical properties of noble gases

  • State: All noble gases are colorless, odorless gases at room temperature.
  • Boiling point: Noble gases have very low boiling point which increases with atomic mass.
  • Inert nature: Because of their complete valence electron shell, the noble gases are almost completely inert at standard conditions.

Visualizing the trend

Let's look at the boiling point trend using another example:

Element: He Ne Ar Kr Xe Rn Boiling Point (°C): -269 -246 -186 -152 -108 -62
Element: He Ne Ar Kr Xe Rn Boiling Point (°C): -269 -246 -186 -152 -108 -62
He by AR Sl Ze boiling point of noble gases

The noble gases show a marked increase in their boiling points with increasing atomic number, due to an increase in van der Waals forces.

Chemical properties of noble gases

  • Inertness: Noble gases rarely participate in chemical reactions under standard conditions. This characteristic is a result of their completely filled valence shell.
  • Compatibility: Since noble gases do not easily form compounds, they are commonly used to provide inert atmospheres in scientific experiments.

Example of use

Helium is often used to fill balloons because it is non-flammable and is lighter than air, allowing the balloons to float.

Application of halogens and noble gases in daily life

Halogens

  • Fluorine: Used as fluoride in toothpaste to help prevent tooth decay.
  • Chlorine: Used as a disinfectant in swimming pools and water treatment facilities.
  • Bromine: It is used in fire retardants and some medicines.
  • Iodine: Essential for thyroid function in humans and used in antiseptics.

Noble gases

  • Helium: Besides its use in balloons, helium is also used in cryogenics and MRI machines.
  • Neon: Famous for the bright neon signs used in advertising.
  • Argon: It is used in incandescent and fluorescent light bulbs to prevent oxidation of the filament.

Conclusion

Halogens and noble gases are important elements with distinct characteristics and various applications in a variety of fields. Their unique physical and chemical properties make them invaluable in both industrial and everyday settings. By understanding the trends and behaviors of these groups, chemists can continue to leverage their properties for innovation and discovery.


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Halogens and Noble Gases

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