chemistry notes

Chemistry Overview

Scientific Method

  • Asking questions: how, what, when, who, which, why, where.

  • Steps:

    • Do research.

    • Construct the hypothesis ("if, then" statement).

    • Test your hypothesis.

    • Analyze your data.

    • Share your results.

States of Matter

  • Three states of matter:

    • Solid: particles are still.

    • Liquid: particles are far apart.

    • Gas: particles are everywhere.

Chemistry Fundamentals

Plasma

  • Composed of protons and electrons (charged and neutral particles).

Chemical Change vs. Physical Change

  • Chemical Change: Creates a new substance.

    • Examples:

      • Rusting iron.

      • Baking a cake.

      • Mixing vinegar and baking soda.

  • Physical Change: Does not create a new substance.

    • Examples:

      • Crushing a can.

      • Tearing paper.

      • Boiling water.

Sir William Crookes

  • Accidental discovery of the cathode ray led to the invention of the TV.

  • Cathode rays consist of streams of charged particles carrying negative charges.

Periodic Table and Atomic Structure

Periodic Law

  • Statement of repetition of chemical and physical properties of elements arranged by increasing atomic number.

Atoms

  • Smallest particle of an element retaining its properties.

  • Visible using a scanning tunneling microscope (STM).

Atomic Mass

  • The atomic weight of an element, arranged in groups/families and periods by increasing atomic number.

Metals

  • Generally shiny, solid at room temperature, good conductors of heat and electricity.

  • Most are malleable (can be pounded into thin sheets) and ductile.

Specific Groups of Elements

  • Alkali Metals (Group 1): Highly reactive; usually found in compounds with other elements (e.g., Na, Li).

  • Alkaline Earth Metals (Group 2): Highly reactive, examples include calcium and magnesium (used in electronics).

  • Halogens (Group 17): Highly reactive nonmetals.

  • Noble Gases (Group 18): Extremely unreactive, used in lasers (e.g., neon lasers).

Historical Figures in Chemistry

Dmitri Mendeleev

  • Created the first periodic table in 1869, arranged elements by increasing atomic mass.

  • Noted repeating properties every eighth element (Law of Octaves).

Lothar Meyer

  • Demonstrated connection between atomic mass and properties of elements; arranged them by increasing atomic mass.

Henry Moseley

  • Discovered atomic number, leading to the arrangement of elements by increasing atomic number.

Electron Structure and Orbitals

Definition of Electrons and Orbitals

  • Electrons: Negative particles found in various energy levels.

  • Orbitals: Areas within the shells where electrons reside.

Orbital Types

  • S Orbital: 1 orbital, holds 2 electrons.

  • P Orbital: 3 orbitals, holds 6 electrons.

  • D Orbital: 5 orbitals, holds 10 electrons.

  • F Orbital: 7 orbitals, holds 14 electrons.

Electron Configuration

  • Arrangement of electrons around the nucleus based on energy levels.

  • Total electrons = atomic number.

  • Electrons fill lowest energy levels first (Aufbau principle).

Chemical Bonds and Properties

Representative Elements

  • Groups 1, 2, and 13-18 possess a wide range of properties; known as main group elements.

  • Transition elements (Groups 3-12) divided into transition metals and inner transition metals.

Inner Transition Metals

  • Lanthanide Series: F block elements from period 6 after lanthanum.

  • Actinide Series: F block elements from period 7 after actinium.

Chemical Bonds

  • Cation: Positively charged ion.

  • Anion: Negatively charged ion.

  • Octet Rule: Atoms gain, lose, or share electrons to achieve a full set of 8 valence electrons.

Naming Conventions

  • Mono, Di, Tri, Tetra, Penta, Hexa, Hepta, Octa, Nona, Deca (prefixes for molecular compounds).

Types of Chemical Bonds

  • Ionic Bonds: Occur between metal and non-metal (e.g., NaCl).

  • Covalent Bonds: Occur when atoms share electrons to achieve stability.

  • Metallic Bonds: Occur with metal atoms; electrons are delocalized through the metal lattice.

  • Hydrogen Bonds: Formed when a hydrogen atom covalently bonded to an electronegative atom is attracted to another electronegative atom's lone pair.

Distillation

  • Process of converting a liquid into vapor and back into liquid.