Chemistry - Basic Elements

Definition of an Element

• Element: A fundamental chemical substance that cannot be broken down into simpler substances through chemical processes.
• Atoms in an element: have the same number of protons, a core concept for understanding elements.

Historical Development of the Concept of Elements

Overview Table

Era/Philosophy	Key Concepts
Ancient Greeks (e.g., Plato, Aristotle)	Classic elements like earth, water, air, fire
Alchemy	Pursuit of transformation and transmutation

Historical Figures

• John Dalton: Introduced the atomic theory, proposing that elements comprise unique atoms.
• Dmitri Mendeleev (1869): Developed the periodic table, arranging elements by atomic mass.

Antoine Lavoisier's Contributions

• Antoine Lavoisier (late 18th century): A leader in modern chemistry, he emphasised the Law of Conservation of Mass.
• Lavoisier identified 33 elements and differentiated between metals and non-metals, forming the basis for contemporary chemistry.

Modern Definition and Advancements

• Significant Advancements:
  • John Dalton: Established atomic theory, a crucial development in understanding atoms and their interactions.
  • Dmitri Mendeleev: Provided the periodic classification that organises elements based on properties and atomic mass.

Symbol and Nomenclature Standards

Standardisation Overview

• Standardising element symbols: Standardising element symbols is essential for scientific discussion.
• Role of IUPAC:
  • The International Union of Pure and Applied Chemistry (IUPAC) ensures uniformity.
• Benefits of Standardisation:
  • Establishes a universal language for scientists worldwide.
  • Facilitates the exchange of scientific information without ambiguity.
  • Enhances understanding across diverse cultures and languages.

Historical and Linguistic Origins of Symbols

• Symbol Origins:
  • Many symbols derive from Latin or other languages, reflecting the element's discovery or historical use.
  • Example: 'Au' for gold is derived from Latin 'Aurum'.

IUPAC Naming Procedures

• Naming Overview:
  • IUPAC employs a rigorous system for naming newly discovered elements.
• Case Study: Element 114:
  • Named Flerovium (Fl) to honour the Flerov Laboratory of Nuclear Reactions.
  • Reflects cultural and scientific recognition within the name.

Introduction to the Periodic Table

• Engaging Opening: How does the periodic table foresee the properties of elements?

• Purpose and Overview: The periodic table is organised by atomic number and properties, allowing scientists to understand elemental relationships.
• Expanded Historical Context: The table's evolution underscores significant milestones, from early classification attempts to current refinements.

Structure of the Periodic Table

• Groups and Periods:
  • Groups as Families: Consider groups as families sharing common characteristics.
    • Real-world example: Group 1 metals react intensely with water, often explosively, underscoring their high reactivity.
  • Trends Across Periods:
    • Changes include increasing electronegativity and decreasing atomic size.
  • Applications: Recognising these trends aids in predicting element reactivity.

Historical Development

• Profiles of Key Figures:
  • Dmitri Mendeleev: Predicted unknown elements through his innovative arrangement.
  • Henry Moseley: Used atomic numbers to refine the organisation of the table.

Classification of Elements

Definition of Categories

• Metals: Known for high electrical conductivity, lustre, ductility, and malleability.
  • Examples: Iron, Copper, Aluminium.

• Non-Metals: Usually exhibit poor conductivity, low lustre, and can exist in various states (solid, liquid, gas).
  • Examples: Carbon, Sulphur, Oxygen.

• Metalloids: Possess properties intermediate between metals and non-metals, crucial for their semi-conductive capabilities in technology.
  • Examples include Silicon and Arsenic.

Key Properties of Elements

• Atomic Radius:
  • Definition: The distance from the nucleus to the outermost electron.
  • Trend Across Periods:
    • Typically decreases.
    • Reason: Increasing nuclear charge.
  • Trend Within Groups:
    • Increases down a group.
    • Reason: Addition of electron shells.

• Electronegativity:
  • Definition: Reflects an atom's ability to attract electrons within a bond.
  • Trend Across Periods:
    • Increases across a period.
    • Reason: Stronger nuclear charge.
  • Trend Within Groups:
    • Decreases down a group.
    • Reason: Increased atomic radius and electron shielding.

• Ionisation Energy:
  • Definition: The energy required to remove an electron from an atom.
  • Trend Across Periods:
    • Generally increases.
    • Reason: Stronger attraction between the nucleus and outer electrons.
  • Trend Down Groups:
    • Decreases down a group.
    • Reason: Larger radii and more electron shielding.