Atomic Structure and Periodic Trends Overview

Sep 9, 2024

AP Chemistry: Unit 1 Overview

Topics Covered

  • Forms of Matter
  • Definition of an Atom
  • Atomic Structures
  • Isotopes
  • Energy Levels, Shells, and Subshells
  • Electron Configuration
  • Periodic Trends

Definition of an Atom

  • Atoms are the building blocks of all matter.
  • Dalton suggested the existence of atoms.
  • Atoms consist of nucleus (protons and neutrons) and electrons.
  • Protons (+ charge), Neutrons (neutral), Electrons (- charge).
  • Atoms are neutral; same number of protons and electrons.

Atomic Structure

  • Nucleus: Contains protons and neutrons.
  • Electrons orbit the nucleus.
  • Atomic Number: Unique identifier for each element.
  • Atomic Mass = Number of protons + number of neutrons.
  • Example: Carbon has atomic number 6, atomic mass 12.

Isotopes

  • Different forms of the same element with different neutron numbers.
  • Example: Carbon-12 and Carbon-13.
  • Mass spectrometry is used to identify isotopes.
  • Average atomic mass is a weighted average based on isotope abundance.

Forms of Matter

  • Elements: Single type of atom (e.g., O2, N2).
  • Compounds: Made of two or more different atoms (e.g., H2O).
  • Mixtures: Can be homogeneous (uniform composition) or heterogeneous (non-uniform composition).

Measuring Matter

  • Volume: Measured in liters/milliliters.
  • Mass: Measured in grams.
  • Count: Using mole concept (Avogadro's number: 6.022 x 10^23).

Electron Configuration

  • Electrons fill orbitals from lowest to highest energy.
  • Shells (n=1,2,3...) and subshells (s, p, d, f).
  • Diagonal Rule for determining order of filling.
  • Abbreviated configuration using noble gases.

Periodic Trends

  • Atomic Radius: Decreases across a period, increases down a group.
  • Ionization Energy: Increases across a period, decreases down a group.
  • Electron Affinity: Increases across a period.
  • Electronegativity: Increases across a period, decreases down a group.

Summary of Key Concepts

  • Atomic radius is influenced by electron shells and nuclear charge.
  • Ionization energy and electron affinity relate to electron stability and attraction.
  • Understanding isotopes and atomic mass is crucial for calculating molecular formulas.
  • Electron configuration impacts chemical properties and reactivity.

This is a comprehensive overview of Unit 1, focusing on the fundamental concepts of atomic theory and periodic trends.