Recording-2025-02-24T16:00:15.255Z

Nitrite Ion and Acids

• Nitrite Ion (NO2-)

  • This ion forms nitrous acid (HNO2).

  • Importance of recognizing chemical species and associated reactions for the exam.

Expanded Octets

• Definition of Expanded Octet

  • More than eight electrons surrounding the central atom.

  • Common in elements from the third period and beyond.

• Example: Sulfur Tetrafluoride (SF4)

  • Central atom (S) surrounded by four fluorine (F) atoms.

  • SF4 is an illustration of an expanded octet since sulfur can accommodate more than eight electrons.

  • Calculation of total electrons around central atom: 6 (from fluorines) + 1 (from sulfur) = 7 around sulfur.

  • Analysis includes electron geometry and molecular geometry based on electron groups.

Resonance Structures

• Understanding Resonance

  • Example with oxygen atoms yielding a total of 12 electrons.

  • Addition of real electrons helps to assess electron distribution.

• Formal Charge Calculation

  • For fluorine: 7 valence electrons, with non-bonding and bonding electrons resulting in formal charge calculations.

  • Formula: ( ext{Formal Charge} = ext{Valence Electrons} - ext{Nonbonding Electrons} - \frac{1}{2} ext{Bonding Electrons} )

  • Example for Fluorine shows positive formal charge when balancing non-bonding and bonding.

Quantum Numbers and Atomic Structure

• Principal Quantum Number (n)

  • Corresponds to the row in the periodic table. For instance, n=1 corresponds to the first row.

• Azimuthal Quantum Number (l)

  • Represents the shape of orbitals with possible values based on n. E.g., there is one s orbital and three p orbitals for n=2.

• Orbitals Overview

  • P orbitals: px, py, pz aligned to x, y, z axes respectively.

  • D orbitals are more complex in shape and arrangement.

• Last Electron Configuration

  • Determining the quantum numbers for the last added electron such as for hydrogen (1s) or chlorine (starting from 1s2).

• Electron Spin and Configuration

  • Each electron can have spin quantum numbers of +1/2 or -1/2; important in orbital filling.

  • Example of 4s orbital usage emphasizes how quantum numbers are determined based on electron arrangement.

Practice and Application

• Worksheets and structures for practicing molecular geometries and resonance are crucial for mastering the content.