Atomic Structures

Atomic Structure Model

  • Basic Concepts

    • Atomic structure involves various subatomic particles including protons, neutrons, and electrons.

  • Cloud Model

    • Visualizes electrons as floating around the nucleus, forming a cloud-like structure.

    • Electrons occupy distinct energy levels, pictured as steps on a ladder.

  • Subatomic Particles

    • Protons

    • Charge: Positive (+)

    • Location: Nucleus

    • Significance: Determines the atomic number of an element.

    • Electrons

    • Charge: Negative (-)

    • Location: Outside of the nucleus

    • Mass: Minimal; does not significantly affect the mass of an element.

    • Behavior: The more electrons, the more negatively charged the atom becomes.

    • Neutrons

    • Charge: No charge (neutral)

    • Significance: Contributes to the mass of the atom without affecting its charge.

  • Using the Periodic Table

    • Atomic Number: Whole number found in an element's box on the periodic table, represents the number of protons.

    • Atomic Mass: Decimal number that reflects the average mass of all isotopes of an element.

    • Rounded using standard rules (5 and above rounds up, 4 and below rounds down).

  • Calculating Neutrons

    • Formula:
      Number of Neutrons=Atomic Mass (rounded)−Atomic Number\text{Number of Neutrons} = \text{Atomic Mass (rounded)} - \text{Atomic Number}

Example of Atomic Composition

Carbon (C)

  • Atomic Number: 6

  • Protons: 6

  • Neutrons: 12 (atomic mass) - 6 (atomic number) = 6

  • Atomic Mass: 12.011

Gold (Au)

  • Protons: 79

  • Atomic Mass: 196.967

  • Neutrons: 197 (atomic mass) - 79 (atomic number) = 118

Lead (Pb)

  • Protons: 82

  • Neutrons: 125

Silver (Ag)

  • Protons: 47

  • Neutrons: 61

Charged Atoms & Ions

  • Ion: A charged atom that occurs from the loss or gain of electrons.

    • Positive Ion (Cation): Formed by losing electrons.

    • Examples:

      • Sodium (Na) loses 1 electron to become Na⁺.

    • Negative Ion (Anion): Formed by gaining electrons.

    • Examples:

      • Chlorine (Cl) gains 1 electron to become Cl⁻.

  • Role of Neutrons: Neutrons cannot be changed to affect charge.

Molecular Formulas

  • General Rules

    • Each capital letter in a molecular formula represents a new element.

  • Examples:

    • Water (H₂O)

    • Composition: 2 Hydrogen (H), 1 Oxygen (O)

    • Iron Oxide (Fe₂O₃)

    • Composition: 2 Iron (Fe), 3 Oxygen (O)

    • Calcium Nitrate [Ca(NO₃)₂]

    • Composition: 1 Calcium (Ca), 2 Nitrogen (N), 6 Oxygen (O)

    • Aluminum Carbonate [Al₂(CO₃)₃]

    • Composition: 2 Aluminum (Al), 3 Carbon (C), 9 Oxygen (O)

Chemical Reactions

  • Example Reaction:

    • O<em>2(g)+2HightarrowH</em>2\text{O}<em>2 (g) + 2H ightarrow H</em>2

    • Indicates the reactants and products participating in the reaction, where coefficients indicate the number of molecules/atoms involved.