Elements, Compounds, and Mixtures

This study guide covers the fundamental concepts of elements, compounds, and mixtures, including definitions, properties, relationships, and examples.

Atoms: The tiny particles that make up matter. They are incredibly small, measured in nanometers.
- Measurement of Atoms: 1 nanometer (nm) = 1 billionth of a meter (1 ext{ nm} = 1 imes 10^{-9} ext{ m}).
- Example Calculation:
  - Thickness of a nickel = 2 mm = 0.002 m.
  - Converting to nanometers:
  - 1 ext{ m} = 1,000,000,000 ext{ nm}
  - Calculation:
    - 1,000,000,000 ext{ nm} imes 0.002 ext{ m} = 2,000,000 ext{ nm}
  - A nickel's thickness is approximately 2,000,000 nanometers, illustrating the vast difference in scale between everyday objects and atoms.
Size Reference: Atoms are analogous to the size of a red blood cell in a scale comparison.

Definition: Elements are the simplest substances that cannot be broken down any further by physical or chemical means.
- Each element has unique physical and chemical properties that allow them to be distinguished:
  - Example: Uranium is radioactive, iron is magnetic.
- Representation: Elements are represented using 1 or 2 letter symbols (e.g., (H) for hydrogen, (O) for oxygen).
Composition of Matter: All matter is made up of elements.

Atoms: The basic unit of a chemical element, consisting of:
- Nucleus: Positively charged center.
- Electron Cloud: Surrounding the nucleus is a cloud of negatively charged electrons.
Molecules: Groups of two or more atoms held together by chemical bonds.
- Definition: The smallest unit of a chemical compound that can participate in a chemical reaction, retaining the properties of the substance.
Chemical Bond: A force of attraction between two atoms, which allows atoms to combine and form molecules.

Compounds: Molecules that consist of two or more elements that are chemically combined.
- Examples of Compounds: Water (H₂O), calcium oxide (CaO), glucose (C₆H₁₂O₆).
- Relation: All compounds are molecules, but not all molecules are compounds (e.g., single atoms of elements like O are not molecules).

Common Molecules Examples:
- Water (H₂O)
- Nitrogen (N₂)
- Ozone (O₃)
- Calcium Oxide (CaO)
- Glucose (C₆H₁₂O₆)
- Table Salt (NaCl)
Non-Molecule: A single atom of an element (e.g., O) is not a molecule because molecules form when atoms bond with other atoms.

Compounds consist of 2 or more elements chemically combined in a set ratio, leading to unique properties different from those of the individual elements.
- Chemical Formula: Represents the elements in a compound and the ratios of the atoms present.
  - Example Ratios:
    - Carbon Dioxide: (CO_2)
    - Carbon Monoxide: (CO)
    - Sucrose: (C{12}H{22}O_{11})
Types of Compounds: The two main types of compounds are ionic and covalent compounds.

Definition: A mixture is a physical combination of two or more substances that are not chemically combined.
- Pure Substance: A single substance made up of only one element or compound.
- Types of Mixtures:
  - Heterogeneous Mixture: The components are easily separable, and their parts are visible.
  - Homogeneous Mixture: The components are not easily separable, and the different parts are hard to distinguish.
- Property Retention: Mixtures retain the properties of those substances that make them up.
  - Example: Strawberry milkshakes maintain the taste and properties of strawberries because whole strawberries are included in the mixture.

Chemical Name: The way a chemist describes a substance, generally naming the elements that compose it.
Common Name: The everyday identification of a substance.
Chemical Formula: Serves as a code indicating which elements are connected and how many atoms of each are present.

Name Comparisons:
- Dihydrogen Monoxide → Water → H₂O
- Acetic Acid → Vinegar → CH₃COOH
- Sodium Chloride → Table Salt → NaCl
- Sucrose → Sugar → C₆H₁₂O₆
- Sodium Hypochlorite → Bleach → NaClO
- Acetone → Acetone → C₃H₆O