Wednesday, 09/02 key points

Fundamental Atomic Structure and Subatomic Particles

  • Atomic Number (ZZ):

    • Defined as the total number of protons in an atom's nucleus.

    • Calculated using the formula:     Z=A−NZ = A - N    

      •  where ZZ is the atomic number, AA is the mass number, and NN is the total number of neutrons.

  • Subatomic Particles:

    • Protons: Positively charged particles located in the nucleus.

      • Determine the element's identity

    • Electrons: Negatively charged particles located outside the nucleus.

      • determine the elements chemical behavior.

    • Neutrons: Neutrally charged particles located in the nucleus.

      • Determine the stability of the atom.

Atomic Mass, Mass Number, and Isotopes

  • Mass Number (AA):

    • Defined as the sum of the total number of protons and neutrons in an atom.

    • Calculated using the formula:     A=Protons+NeutronsA = \text{Protons} + \text{Neutrons}

    • Characteristics:

      • Always a whole integer.

      • Represents a specific single isotope.

      • Does not appear on the periodic table.

  • Atomic Mass (Atomic Weight):

    • Defined as the weighted average mass of all naturally occurring isotopes of an element, based on their natural percent abundance.

    • Expressed in atomic mass units (amu\text{amu}), which represent extremely small mass values.

    • Appears on the periodic table.

  • Isotopes:

    • Defined as atoms of the same element that differ in their number of neutrons, but contain the exact same number of protons.

    • Written in the format: "element" - "mass number" (for example, Uranium-240).

      • Specific Examples:

      • Silicon-28 (28Si^{28}\text{Si})

      • Silicon-29 (29Si^{29}\text{Si})

Ion Formation, Charge, and Oxidation Numbers

  • Formation of Ions:

    • Neutral atoms transform into ions through the loss or gain of electrons.

    • Formal charge is calculated using the formula: Charge=Protons−Electrons\text{Charge} = \text{Protons} - \text{Electrons}

  • Types of Ions:

    • Cation: A positively charged ion formed when a neutral atom loses 11 or more electrons (which carry a negative charge).

      • Example: A neutral hydrogen atom (H\text{H}) loses its 11 electron to become a hydrogen cation (H+\text{H}^+ ).

    • Anion: A negatively charged ion formed when a neutral atom gains 11 or more electrons.

      • Example: A neutral oxygen atom (O\text{O}) gains 22 electrons to become an oxide anion (O2−\text{O}^{2-}), resulting in a total of 1010 electrons.

  • Notations for Ionic Charge vs. Oxidation Number:

    • Formal Ionic Charge: Indicated with the number before the sign (for example, 2−2- or 2+2+).

    • Oxidation Number: Indicated with the number after the sign (for example, −2-2 or +2+2).

Nuclear Symbolism and Isotope Notation

  • Full Nuclear Symbol Format:

    • Standard format:     ZAEcharge^{A}_{Z}\text{E}^{\text{charge}}

    • Symbol Components:

    • E\text{E}: Element symbol, which determines the identity and chemical behavior.

    • AA: Mass number, located at the top left.

    • ZZ: Atomic number, located at the bottom left (frequently omitted as the element symbol uniquely defines the atomic number).

    • charge\text{charge}: Formal ionic charge, located at the top right.

Physical Properties: Density

  • Definition and Formula:

    • Density measures the ratio of mass to volume for a given substance.

    • Calculated using the formula:     Density=MassVolume\text{Density} = \frac{\text{Mass}}{\text{Volume}}