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💏intro to chemistry review

AsH3

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

AsH3, also known as arsine, is a colorless, flammable, and highly toxic gas. It is a covalent compound composed of one arsenic (As) atom bonded to three hydrogen (H) atoms. AsH3 is an important compound in the context of molecular structure and polarity.

5 Must Know Facts For Your Next Test

  1. AsH3 has a trigonal pyramidal molecular geometry, with the arsenic atom at the center and the three hydrogen atoms at the vertices.
  2. The bond angle in AsH3 is approximately 91.3 degrees, which is slightly less than the ideal tetrahedral angle of 109.5 degrees.
  3. The presence of three bonding pairs and no lone pairs of electrons around the central arsenic atom results in the trigonal pyramidal shape.
  4. AsH3 is a polar molecule due to the unequal distribution of electrons between the arsenic and hydrogen atoms, with the arsenic atom having a partial positive charge and the hydrogen atoms having a partial negative charge.
  5. The polarity of AsH3 is responsible for its high reactivity and ability to participate in various chemical reactions.

Review Questions

  • Explain the molecular geometry of AsH3 and how it is determined by the number of bonding pairs and lone pairs of electrons around the central arsenic atom.
    • The molecular geometry of AsH3 is trigonal pyramidal, with the arsenic atom at the center and the three hydrogen atoms at the vertices. This geometry is determined by the presence of three bonding pairs of electrons and no lone pairs of electrons around the central arsenic atom. According to the Valence Shell Electron Pair Repulsion (VSEPR) theory, the arrangement of the bonding pairs and lone pairs of electrons around the central atom determines the overall shape of the molecule. In the case of AsH3, the three bonding pairs of electrons occupy more space than the lone pairs, resulting in the trigonal pyramidal geometry.
  • Describe the polarity of the AsH3 molecule and explain how it is related to the unequal distribution of electrons between the arsenic and hydrogen atoms.
    • AsH3 is a polar molecule due to the unequal distribution of electrons between the arsenic and hydrogen atoms. The electronegativity difference between arsenic and hydrogen results in the arsenic atom having a partial positive charge, while the hydrogen atoms have a partial negative charge. This unequal distribution of electrons creates a dipole moment within the molecule, making AsH3 polar. The polarity of AsH3 is an important property that influences its chemical reactivity and the way it interacts with other molecules.
  • Analyze how the molecular structure and polarity of AsH3 contribute to its unique chemical properties and potential applications.
    • The trigonal pyramidal molecular geometry and polarity of AsH3 are key factors that determine its chemical properties and potential applications. The polar nature of the molecule allows it to participate in various chemical reactions, such as acid-base reactions and nucleophilic substitutions. Additionally, the unequal distribution of electrons in AsH3 makes it a good reducing agent, with the potential to be used in semiconductor manufacturing and other industrial processes. Understanding the relationship between the molecular structure, polarity, and chemical reactivity of AsH3 is crucial for predicting its behavior and exploring its practical applications in chemistry and materials science.