Chemistry: Electrons, Shells, and Periodic Trends

Coulomb's Law

  • Describes the force between charged particles.
  • Key points:
    • More protons lead to a greater positive nuclear charge, resulting in electrons being pulled more toward the nucleus.
    • Strength of the force is proportional to the quantity of charge:
    • $1 \text{ unit of charge} = \text{ Stronger Force}$.

Electron Shells

  • Electrons occupy distinct energy levels known as shells, designated as:
    • Shell 1: 1s
    • Shell 2: 2s, 2p
    • Shell 3: 3s, 3p
    • Shell 4: 4s, 4p, 4d
  • As the number of shells increases, the distance from the nucleus increases, reducing the attraction between the nucleus and electrons.

Subshells and Orbitals

  • Each shell has subshells denoted by the letters s, p, d, f, etc.
  • Orbitals are the most probable regions where electrons can be found:
    • Type of orbital and maximum electrons:
    • s orbital: 1 orbital, 2 max electrons
    • p orbital: 3 orbitals, 6 max electrons
    • d orbital: 5 orbitals, 10 max electrons
    • f orbital: 7 orbitals, 14 max electrons

Electron Configuration and Excited States

  • Electron configurations of elements show the arrangement of electrons in their orbitals.
  • Example: For an element with 20 electrons (e.g., Calcium):
    • The configuration may be influenced by exciting electrons to higher orbitals. If one electron moves to a higher energy level, it is in an excited state.
  • Notation for e- configuration in terms of the number of electrons in each orbital, e.g.,
    • 1s\^2, 2s\^2, 2p\^6, 3s\^2, 3p\^6, 4s\^2, 3d\^10, 4p\^5.

Trends in the Periodic Table

  • From left to right across a period (row):
    • Nuclear charge increases, affecting attraction to electrons.
  • From top to bottom in a group (column):
    • More electron shells mean electrons are further from the nucleus, reducing effective nuclear charge felt by outer electrons.

Summary of Electron Shell and Valence Behavior

  • Valence electrons are crucial in determining how an atom will bond with others.
  • Group behavior (same as vertical column) and period behavior (same as horizontal row) are influenced by the electron shell arrangement and the respective distances from the nucleus.