Group 17 and 18 Elements
Halogen trends, interhalogens, bleaching powder and the chemistry of noble gases. (Chemistry › p-Block Elements, NEET UG syllabus.)
What is Group 17 and 18 Elements?
Elements of Group 17 (F, Cl, Br, I, At), highly reactive non-metals that readily form salts.
Key formula / rule: Bleaching Powder
Key points
- Describe the general characteristics, physical, and chemical trends of Group 17 elements.
- Explain the reactivity, oxidizing nature, and common oxidation states of halogens.
- Discuss the preparation, properties, and uses of interhalogen compounds and bleaching powder.
- Describe the general characteristics and trends of Group 18 elements.
Common exam trap
Confusing the order of electron gain enthalpy (Cl > F is correct).
Definitions
- Term
Halogens
- Meaning
Elements of Group 17 (F, Cl, Br, I, At), highly reactive non-metals that readily form salts.
- Term
Noble Gases
- Meaning
Elements of Group 18 (He, Ne, Ar, Kr, Xe, Rn), characterized by their stable, completely filled valence electron shells and general inertness.
- Term
Interhalogen Compounds
- Meaning
Compounds formed between two different halogens, generally more reactive than individual halogens (except F₂).
- Term
Bleaching Powder
- Meaning
A mixed salt of calcium, Ca(OCl)Cl, used as a bleaching agent, disinfectant, and oxidizing agent.
- Term
Electron Gain Enthalpy
- Meaning
The energy change that occurs when an electron is added to a neutral isolated gaseous atom to form a negatively charged ion.
Learning objectives
Describe the general characteristics, physical, and chemical trends of Group 17 elements.
Explain the reactivity, oxidizing nature, and common oxidation states of halogens.
Discuss the preparation, properties, and uses of interhalogen compounds and bleaching powder.
Describe the general characteristics and trends of Group 18 elements.
Explain the inertness of noble gases and the conditions for compound formation.
Discuss the preparation, properties, and structures of important Xenon compounds (fluorides, oxides, oxyfluorides).
Formulae
- Name
Bleaching Powder
- Note
Also represented as CaOCl₂
- Expression
Ca(OCl)Cl
- Name
General Interhalogen Compounds
- Note
A is larger halogen, X is smaller halogen
- Expression
AX, AX₃, AX₅, AX₇
- Name
Xenon Difluoride
- Note
Linear structure
- Expression
XeF₂
- Name
Xenon Tetrafluoride
- Note
Square planar structure
- Expression
XeF₄
- Name
Xenon Hexafluoride
- Note
Distorted octahedral structure
- Expression
XeF₆
- Name
Xenon Trioxide
- Note
Pyramidal structure
- Expression
XeO₃
- Name
Krypton Difluoride
- Note
- Expression
KrF₂
Prerequisites
Basic knowledge of periodic trends (atomic size, electronegativity, ionization enthalpy).
Understanding of chemical bonding, including VSEPR theory and hybridization.
Concepts of redox reactions and oxidation states.
Basic acid-base chemistry.
Common mistakes
Confusing the order of electron gain enthalpy (Cl > F is correct).
Incorrectly stating F₂ has the highest bond dissociation enthalpy (Cl₂ > Br₂ > F₂ > I₂).
Forgetting the structures of interhalogen compounds or Xenon compounds.
Misremembering the formula or preparation of bleaching powder.
Assuming all noble gases form compounds.
Incorrectly predicting products of hydrolysis of Xenon fluorides.
Keywords
Halogens
Noble Gases
Fluorine
Chlorine
Bromine
Iodine
Xenon
Krypton
Interhalogens
Bleaching Powder
Electron Gain Enthalpy
Bond Dissociation Enthalpy
Oxidation States
VSEPR Theory
Hydrolysis
Oxidizing Agent
Periodic Trends
Practice preview
What is the chemical formula for bleaching powder?…
easy
Xenon difluoride (XeF2) reacts with antimony pentafluoride (SbF5) to form an ionic compound. What is the geometry of the cationic species formed in this reaction?…
hard
Why are noble gases generally unreactive?…
medium