Textbook Question
Describe the molecular geometry of:
(a) H2Se
Ch.22 - The Main Group Elements
Chapter 22, Problem 59
In the following compounds, is hydrogen present as H+, H-, or a covalently bound H atom? (b) RbH (d) GeH4
Verified step by step guidance1
Step 1: Identify the type of compound RbH is. Rb (rubidium) is an alkali metal, which typically forms ionic compounds. In ionic compounds, hydrogen can exist as a hydride ion (H-).
Step 2: Analyze the electronegativity difference between Rb and H. Rubidium has a much lower electronegativity compared to hydrogen, suggesting that hydrogen will gain an electron, forming H-.
Step 3: Conclude that in RbH, hydrogen is present as H- because it forms an ionic bond with rubidium, where rubidium donates an electron to hydrogen.
Step 4: Identify the type of compound GeH4 is. Ge (germanium) is a metalloid, and GeH4 is a covalent compound, similar to methane (CH4).
Step 5: Conclude that in GeH4, hydrogen is covalently bound to germanium, as the electronegativity difference is not sufficient to form ions, resulting in shared electrons between Ge and H.
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Hydrogen Ion (H+)
H+ represents a hydrogen ion, which is a proton that has lost its electron. In this form, hydrogen carries a positive charge and is often found in acids or ionic compounds. Understanding when hydrogen exists as H+ is crucial for analyzing the acidity or basicity of a compound.
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Hydride Ion (H-)
H- is known as a hydride ion, which occurs when hydrogen gains an extra electron, resulting in a negative charge. This form of hydrogen is typically found in ionic compounds with metals, where it acts as a reducing agent. Recognizing the presence of H- is important for understanding the reactivity and bonding in certain compounds.
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Covalently Bound Hydrogen (H)
Covalently bound hydrogen refers to hydrogen atoms that are bonded to other atoms through covalent bonds, sharing electrons. This is the most common form of hydrogen in organic and inorganic molecules, where it contributes to the molecular structure and properties. Identifying covalently bound hydrogen is essential for understanding molecular geometry and reactivity.
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Related Practice