AP Chemistry Overview: Atomic Structure

Aug 10, 2024

Review flashcards

Understanding AP Chemistry Exam - Unit 1: Atomic Structure and Properties

Overview

  • Comprehensive review of Unit 1 topics for the AP Chemistry exam.
  • Focus on atomic structure, properties, and related concepts.
  • Summary of essential topics: moles, molar mass, electron configurations, periodic trends, etc.

Basic Atomic Concepts

Atoms and Elements

  • Atoms: Smallest unit of an element.
  • Elements: Substance made of one type of atom (e.g., copper).
  • Protons: Define the element (e.g., Carbon = 6 protons).
  • Molecules: Atoms combined via chemical bonds. Can be elements (e.g., O2) or compounds (e.g., CO2).

Pure Substances and Mixtures

  • Pure Substances: Single type of element or compound (e.g., sodium metal, water).
  • Mixtures: Combination of different elements or compounds (e.g., air, saltwater).
    • Homogeneous: Evenly mixed substances (e.g., sugar in water).
    • Heterogeneous: Unevenly mixed substances (e.g., oil and water).

Atomic Structure

Subatomic Particles

  • Protons and Neutrons: Located in nucleus, mass ~1.67 x 10^-24 grams.
  • Electrons: Surround nucleus, mass ~9.1 x 10^-28 grams.
  • Electric Charge: Protons (+), Electrons (-), Neutrons (neutral).

Atomic and Mass Numbers

  • Atomic Number: Number of protons in nucleus (defines the element).
  • Mass Number: Total number of protons and neutrons.
  • Isotopes: Atoms with the same number of protons but different numbers of neutrons (e.g., Carbon-12, Carbon-13, Carbon-14).
  • Atomic Mass: Average mass of an element's isotopes, considering their relative abundance.
  • Ions: Atoms that gain or lose electrons (Cations: + charge, Anions: - charge).

Mass Spectroscopy

  • Purpose: Determine masses of isotopes and their abundances.
  • Process: Vaporize sample, ionize, pass through magnetic field, detect deflection.

Mole Concept

Definition and Molar Mass

  • Mole: A number (6.022 x 10^23, Avogadro’s number) for counting atoms/molecules.
  • Molar Mass: Mass of one mole of a substance (in grams).

Conversions

  • Convert between grams and moles using molar mass.
    • Example: 28.35 grams of glycine (C2H5O2N) is 0.38 moles.

Empirical and Molecular Formulas

  • Percent Composition: Percent of each element’s mass in a compound.
  • Empirical Formula: Lowest whole number ratio of atoms in a compound.
  • Molecular Formula: Actual number of atoms in a molecule (determined using molecular mass).
    • Example: Empirical formula CH2, molecular mass 42 g/mol, molecular formula C3H6.

Electron Configuration

Quantum Numbers and Orbitals

  • Principal Quantum Number (n): Energy level, shell.
  • Angular Momentum Quantum Number (L): Defines type of orbital (s, p, d).
  • Magnetic Quantum Number (mL): Specific orbital within a subshell.
  • Spin Quantum Number (ms): Electron spin (+1/2 or -1/2).

Aufbau Principle and Hund’s Rule

  • Aufbau Principle: Electrons fill lowest energy orbitals first.
  • Hund’s Rule: Electrons fill degenerate orbitals singly before pairing.

Electron Configuration Notation

  • Orbitals filled according to energy levels.
  • Periodic table sections correspond to types of orbitals (s, p, d blocks).
  • Example: Chlorine (Cl) has electron configuration 1s2 2s2 2p6 3s2 3p5.

Periodic Trends

Atomic Radius

  • Definition: Size of an atom, half the distance between nuclei of bonded atoms.
  • Trend: Increases down a group, decreases across a period (left to right).

Ionic Radius

  • Cations: Smaller than their neutral atoms (loss of electrons).
  • Anions: Larger than their neutral atoms (gain of electrons).
  • Isoelectronic Species: Same electron configuration, radius decreases with increasing atomic number.

Ionization Energy

  • Definition: Energy required to remove an electron from an atom.
  • Trend: Decreases down a group, increases across a period (left to right).

Electron Affinity

  • Definition: Energy change when an electron is added to a neutral atom.
  • Trend: Generally increases up and right on the periodic table (excluding noble gases).

Electronegativity

  • Definition: Measure of an atom’s ability to attract electrons in a bond.
  • Trend: Increases up and right on the periodic table (excluding noble gases).

Conclusion

  • Summary of key concepts in atomic structure and properties.
  • Preparation for deeper dives into more complex topics and units.
  • Encouragement to understand fundamental principles for success in AP Chemistry.