Chemistry Basics and Atomic Structure

Chemistry Basics

• Physical properties: Properties that can be determined without changing the substance (e.g., color, smell, melting point).
• Chemical properties: Properties that can only be determined by changing the substance (e.g., flammability, toxicity, reactivity).
• Physical changes: Reversible changes in state (e.g., melting ice, vaporizing water).
• Chemical changes: Non-reversible changes (e.g., burning wood, frying an egg).
• Quantitative observation: Has a numerical value (e.g., 15 kg, a dozen roses).
• Qualitative observation: Does not have a numerical value (e.g., red roses, fishy smell).
• States of matter:
  • Solids: Particles packed closely together, vibrating.
  • Liquids: Particles further apart than solids, flowing past each other.
  • Gases: Particles far apart, moving freely.
  • Plasma: Superhot, high-pressure gas (e.g., the sun).

Atomic Structure

• Subatomic particles:
  • Protons: Positively charged, mass of 1, located in the nucleus.
  • Neutrons: Neutrally charged, mass of 1, located in the nucleus.
  • Electrons: Negatively charged, mass of 1/1838, orbiting the nucleus.
• Element: a type of atom
• Compound: Two or more different atoms bound together (a pure substance).
• Mixture: Combination of different particles in the same space (not bound).

Mixtures and Compounds

• Homogeneous mixture: One phase, looks like one substance (e.g., milk, apple juice).
• Heterogeneous mixture: Multiple phases, different parts are visible (e.g., chicken soup, pizza).

Periodic Table

• Periodic Table: Chart of all elements, arranged by atomic number (number of protons).
• Discoverer: Dmitri Mendeleev.
• Metals: Left of the staircase, want to lose electrons, shiny, conduct electricity.
• Non-metals: Right of the staircase, gain electrons, generally do not conduct electricity.
• Metalloids: Properties of both metals and non-metals, located along the staircase.
• Rows (periods): Tell us how many orbitals an atom has.
• Columns (groups): Tell us how many valence electrons an atom has.

Atomic Properties

• Atomic number: Determines the type of element, equal to the number of protons.
• Atomic mass: Sum of protons and neutrons.
• Isotope: Same element, same number of protons but different number of neutrons (different mass).

Noble Gases

• Non-reactive: Full valence shell.

Alkali and Alkaline Earth Metals

• Alkali Metals: One valence electron, more reactive.
• Alkaline Earth Metals: Two valence electrons.

Types of Bonds

• Ionic Bonds: Formed between metals and non-metals by transferring electrons.
• Covalent Bonds: Formed between non-metals by sharing electrons.

Chemical Reactions

• Synthesis reaction: Two or more substances combine to form a new product.
• Decomposition reaction: One substance breaks down to form two or more products.
• Combustion reaction: Burning something in the presence of oxygen.