IB DP Chemistry: Topic 3 - Periodicity

3.1 The Periodic Table

Essential Idea

• The arrangement of elements in the periodic table allows prediction of electron configuration.

Understandings

• The periodic table is divided into four blocks corresponding to four sublevels: s, p, d, f.
• Consists of groups (vertical columns) and periods (horizontal rows).
  • Period number indicates the outer energy level occupied by electrons.
  • From an element's position, deduce both principal energy level and valence electrons.
• Shows locations of metals, non-metals, and metalloids.

Applications and Skills

• Deduction of electron configuration from an element's position and vice versa.

Classification of Elements and Periodicity in Properties

The Periodic Table of the Elements

• Elements with similar properties are grouped together.

Historical Classifications

• Dobereiner's Law of Triads: Groups of three elements with similar properties; middle element's atomic weight is the arithmetic mean of the others.
• Newlands' Law of Octaves: Elements arranged by increasing atomic weight, every eighth element shares properties with the first.
• Mendeleev's Periodic Table: Based on atomic weights, periodic properties recur at intervals. Predicted elements like Gallium and Germanium.

Modern Periodic Law

• Moseley: Properties of elements are periodic functions of atomic number, not atomic weight.
• Elements with similar properties recur at intervals: magic numbers (2, 8, 8, 18, 32).

Structural Features of the Long Form of the Periodic Table

• Groups: 18 vertical columns
  • Group 1: Alkali metals
  • Group 2: Alkaline earth metals
  • Group 16: Chalcogens
  • Group 17: Halogens
  • Group 18: Noble gases
• Periods: 7 horizontal rows
  • 1st period: Shortest, 2 elements
  • 2nd, 3rd periods: Short, 8 elements each
  • 4th, 5th periods: Long, 18 elements each
  • 6th period: Longest, 32 elements
  • 7th period: Incomplete, currently 26 elements
• Blocks: s, p, d, f blocks based on subshell of valence electron
  • f-block: Lanthanides and Actinides, placed at the bottom

Nomenclature for Elements (Atomic Number > 100)

• IUPAC nomenclature based on numerical roots for digits in atomic numbers.
  • Example: Element 108 is Unniloctium.

Diagonal Relationship

• Certain elements in period 2 (e.g., Li, Be, B) show similarities with diagonal elements in period 3 (e.g., Mg, Al, Si) due to similar ionic radii and polarizing power.

Periodic Properties

• Atomic Size: Distance from nucleus to outermost electrons. Expressed in covalent, Van-der Waals, metallic, ionic radii.
  • Factors: Bond multiplicity, ionic character, nuclear charge.
  • Trend: Increases down a group, decreases across a period.
• Ionization Energy (I.E.): Energy to remove an electron from a gaseous atom.
  • Successive ionization energies increase.
  • Trends: Increases across a period, decreases down a group.
  • Factors: Atomic size, inner-shell electrons, nuclear charge, stable configurations.
• Electron Affinity (EA): Energy change when an electron is added to a gaseous atom.
  • First EA positive, subsequent can be negative due to repulsion.
  • Trends: Increases across a period, decreases down a group.
  • Factors: Nuclear charge, atomic size, stable configurations.
• Electronegativity (EN): Atom's ability to attract shared electrons.
  • Scales: Mulliken, Pauling.
  • Trends: Increases across a period, decreases down a group.
  • Depends on atomic size, nuclear charge, shielding effect, oxidation state, hybridization.

Valency

• Number of electrons gained/lost/shared in compound formation.

Atomic Volume

• Volume occupied by a mole of an element's atoms at melting point.
  • Trends: Decreases across a period, increases down a group.

Acid-Base Behavior of Oxides and Hydroxides

• Depends on ionization energy.
  • Low IE = basic; high IE = acidic.
  • Trends: Basic to acidic across a period, stability increases while reactivity decreases.