Notes for chem

  • Pure Substance: A material made of only one type of particle.

    • Example: Distilled water (H₂O) or copper (Cu).

  • Mixture: A combination of two or more substances that retain their individual properties.

    • Example: Saltwater (a mixture of salt and water) or salad (a mixture of various vegetables).

  • Homogeneous Mixture: A mixture that has a uniform composition throughout.

    • Example: Air or vinegar.

  • Heterogeneous Mixture: A mixture that consists of visibly different substances or phases.

    • Example: Sand and iron filings or a salad.

Location in the Periodic Table:

Metals are located on the left side and the center, while nonmetals are on the right side of the periodic table.

  • Difference between Elements, Compounds, and Molecules:

    • Element: A pure substance that cannot be broken down into simpler substances.

    • Compound: A substance formed when two or more elements are chemically bonded together.

    • Molecule: The smallest unit of a compound that retains the properties of that compound (e.g., H₂O).

  • Physical Properties: Characteristics that can be observed or measured without altering the substance's composition.

    • Example: Color, odor, melting point, and solubility.

  • Chemical Properties: Characteristics that describe a substance's ability to undergo changes that transform it into different substances.

    • Example: Reactivity with acids or flammability.

  • Periodic Table Arrangement:

    • Organized by increasing atomic number, elements in the same column (family) share similar chemical properties, while elements in the same row (period) have the same number of electron shells.

  • Atomic Structure: An atom is made up of protons, neutrons, and electrons. The atomic number indicates the number of protons in the nucleus.

  • Main Families on the Periodic Table to Know:

    • Group 1 (Alkali Metals)

    • Group 2 (Alkaline Earth Metals)

    • Group 17 (Halogens)

    • Group 18 (Noble Gases)

  • Valence Shells: The number of valence shells corresponds to the period number of an element in the periodic table, indicating the number of electron shells surrounding the nucleus.

  • Bohr Diagrams: A visual representation of an atom showing its nucleus and the arrangement of electrons in different energy levels.

  • Naming Compounds and Charges: To determine the charge on a compound, consider the oxidation states of elements; for instance, NaCl consists of Na⁺ and Cl⁻.

  • Atomic Number: The atomic number (Z) represents the number of protons in an atom; neutrons can vary in isotopes, and electrons change to form ions.

  • Ions: The only thing changing in ions are the electrons, which can gain or lose to achieve a full outer shell—leading to positively charged cations or negatively charged anions.

  • Similarities and Differences between Ionic and Covalent Bonding:

    • Ionic Bonding: Involves transfer of electrons from one atom to another resulting in positive and negative ions.

    • Covalent Bonding: Involves sharing of electrons between atoms.

    • Similarities: Both types of bonding generally aim to achieve full valence shells and result in compounds.